Approximation of objects by spheres for multisphere simulations in DEM
ECCOMAS-2012 (04/07/2012)Amberger, Stefan; Friedl, Michael; Goniva, Christoph; Pirker, Stefan; Kloss, Christoph
This paper presents a novel grid-based method to approximate non-convex, closed objects using a finite number of spheres, addressing limitations in simulating granular systems with spherical particles. Implemented in LIGGGHTS, the method enables multi-sphere approximations of objects defined by stereo-lithography files, such as laser-scanned surface data. The process involves grid creation, sphere placement based on grid-point data, volume calculation, and scaling to match the object’s volume. A quality measure is introduced to evaluate approximations. Results demonstrate the method's effectiveness, providing a practical tool for simulating non-spherical particles in discrete element simulations.
Combining Open Source and Easy Access in the field of DEM and coupled CFD-DEM: LIGGGHTS®, CFDEM®coupling and CFDEM®workbench
Computer Aided Chemical Engineering (10/07/2018)Hager, Alice; Kloss, Christoph; Goniva, Christoph
Discrete Element Method (DEM) and its combination with Computational Fluid Dynamics (CFD-DEM) are essential for designing and optimizing particle processes in various industries such as pharmaceuticals, agriculture, and manufacturing. The open source software, CFDEM®coupling and LIGGGHTS®, offer advanced simulation capabilities. However, the complexity of installing and using these tools can be a barrier for many potential users. To address this, the commercial GUI CFDEM®workbench was developed to simplify the use of these powerful simulation tools while maintaining the benefits of open source software. It assists users in installation and setup, facilitating access to sophisticated DEM and CFD-DEM modeling in sectors ranging from steel to plastics production.
Direct Numerical Simulation of a Buoyant Droplet Array
Direct and Large-Eddy Simulation VIII (03/07/2011)Kwakkel, Marcel; Breugem, Wim-Paul; Boersma, Bendiks Jan
This research focuses on Direct Numerical Simulation (DNS) of approximately 1,000 inertial droplets in a turbulent carrier fluid, incorporating physical models for coalescence and breakup. The study addresses the computational challenges of such simulations, demonstrating that their code scales efficiently with increasing numbers of deformable droplets and larger grid sizes. This advancement enhances the understanding of droplet dynamics and turbulence interactions, particularly in clustering regimes where the Stokes number is around 1.
Tree root mounds and their role in transporting soil on forested landscapes
Earth Surface Processes and Landforms (01/05/2014)Hoffman, Benjamin S. S.; Anderson, Robert S.
The study explores how tree roots contribute to soil movement on hillslopes by examining soil mounding around Ponderosa and Lodgepole pine trees in Colorado's Boulder Creek watershed. Soil mounds around these trees show significant vertical displacements up to 20 cm, indicating that tree roots actively displace and mix the surrounding soil. This displacement is not merely due to soil flow around the tree but is caused by root volume expansion in all directions. The study uses a discrete element model (LIGGGHTS) to simulate root growth and the resulting soil mounding, confirming that root growth can substantially alter soil density and topography. This research underscores the importance of root dynamics in soil transport processes on forested slopes.
Decoding the structure of granular and porous materials from speckled phase contrast X-ray images
Optics Express (01/08/2013)Carnibella, R. P.; Kitchen, M. J.; Fouras, A.
The paper discusses a new thermal lens effect utilizing a laser beam with Orbital Angular Momentum (OAM). The study investigates how the OAM properties of a laser can influence the formation of thermal lenses, a phenomenon where the medium's refractive index changes due to temperature gradients caused by laser heating. This research is significant for advancing our understanding of light-matter interactions in optically active and thermal-sensitive environments, providing insights into the dynamic processes involved and potential applications in optical systems.
Correct Boundary Conditions for Turbulent SPH
Advances in Hydroinformatics (12/11/2014)Ferrand, Martin; Violeau, Damien; Mayrhofer, Arno; Mahmood, Omar
This publication discusses the formulation of correct boundary conditions for turbulent flows using the Smoothed Particle Hydrodynamics (SPH) method. It introduces unified and consistent boundary conditions for 2D SPH for weakly compressible flows, covering wall impermeability, wall shear stress, and wall turbulent conditions using the k-ε model. Additionally, it addresses inlet-outlet open boundaries, aiming to enhance the accuracy and applicability of SPH simulations in engineering and physics. This approach is crucial for modeling complex fluid dynamics in various practical and industrial applications.
Eddy interaction model for turbulent suspension in Reynolds-averaged Euler–Lagrange simulations of steady sheet flow
Advances in Water Resources (01/01/2018)Cheng, Zhen; Chauchat, Julien; Hsu, Tian-Jian; Calantoni, Joseph
The article from Elsevier discusses the effectiveness of different treatment regimens for latent tuberculosis infection (LTBI). It aims to provide evidence-based insights to assist policymakers in designing national treatment policies and protocols. The study uses the PRISMA-NMA method to review and synthesize existing data on the efficacy, adherence, and safety of various LTBI treatments, emphasizing the need for tailored approaches to prevent the progression to active tuberculosis.
Characterization of Supersonic Turbulent Combustion in a Mach-10 Scramjet Combustor
AIAA Journal (01/05/2020)Moura, Augusto F.; Gibbons, Nicholas; Wheatley, Vincent; McIntyre, Timothy; Jahn, Ingo
This paper discusses modal decomposition techniques as a tool for simplifying the complex dynamics of fluid flows by breaking them down into fundamental components or modes. These techniques, which include methods like Proper Orthogonal Decomposition and Dynamic Mode Decomposition, are valuable for capturing key dynamic features of fluid systems across various conditions, facilitating more efficient analysis and modeling. This approach is particularly useful in engineering and physics to develop low-dimensional models of complex systems, enhancing both computational and experimental methodologies.
Correction: Characterization of Supersonic Turbulent Combustion in a Mach-10 Scramjet Combustor
AIAA Journal (01/04/2021)Moura, Augusto F.; Gibbons, Nicholas; Wheatley, Vincent; McIntyre, Timothy; Jahn, Ingo
The paper discusses modal decomposition techniques, which simplify the dynamics of fluid flows by breaking them down into fundamental components or modes. These techniques are instrumental for capturing essential dynamic features across various conditions, thereby aiding in the development of low-dimensional models for complex systems. This approach optimizes both computational and experimental methodologies in engineering and physics.
Effects of Oxygen Enrichment on Supersonic Combustion in a Mach 10 Scramjet
AIAA Journal (01/11/2021)Moura, Augusto F.; Gibbons, Nicholas; Wheatley, Vincent; Jahn, Ingo
The paper explores the effects of oxygen enrichment on supersonic combustion in scramjet engines operating at Mach 10. It discusses the benefits of premixing fuel with oxygen to enhance combustion efficiency at high altitudes where oxygen levels are otherwise insufficient. This technique aims to expand the operational envelope of scramjets, traditionally limited by atmospheric oxygen availability, thereby offering a more versatile solution for high-speed aerial and space propulsion systems.
A redefined energy functional to prevent mass loss in phase-field methods
AIP Advances (01/06/2020)Kwakkel, M.; Fernandino, M.; Dorao, C. A.
The article explores an updated energy functional designed to prevent mass loss in phase-field models. The new functional includes terms that account for both bulk energy density and excess energy due to inhomogeneous distribution in the interfacial regions. This redefined energy functional helps in ensuring a proper energy balance while preventing nonphysical bulk diffusion, thus improving the conservation of mass in computational simulations that use phase-field methods.
Improving the applicability of discrete phase simulations by smoothening their exchange fields
Applied Mathematical Modelling (01/05/2011)Pirker, S.; Kahrimanovic, D.; Goniva, C.
This study addresses the limitations of the Discrete Phase Model (DPM) in simulating particle-laden flows, particularly its inability to account for particle collisions and the resulting overestimation of particle dispersion. The authors propose an enhanced DPM approach that incorporates a stochastic collision model to simulate particle-particle interactions. Validation against experimental data demonstrates improved accuracy in predicting particle dispersion and concentration profiles, making this method more reliable for engineering applications involving particulate flows.
Floating electrode optoelectronic tweezers: Light-driven dielectrophoretic droplet manipulation in electrically insulating oil medium
Applied Physics Letters (01/04/2008)Park, Sungyong; Pan, Chenlu; Wu, Ting-Hsiang; Kloss, Christoph; Kalim, Sheraz; Callahan, Caitlin E.; Teitell, Michael; Chiou, Eric P. Y.
The research introduces Floating Electrode Optoelectronic Tweezers (FEOET), a mechanism for manipulating aqueous droplets in electrically insulating oil using light-induced dielectrophoresis. FEOET employs a photoconductive glass layer to create virtual electrodes with direct optical images, enabling light-driven transport of droplets. This technique offers a versatile and efficient method for droplet manipulation in microfluidic applications.
Molecular Dynamics simulation for PBR pebble tracking simulation via a random walk approach using Monte Carlo simulation
Applied Radiation and Isotopes (01/05/2012)Lee, Kyoung O.; Holmes, Thomas W.; Calderon, Adan F.; Gardner, Robin P.
This paper introduces a new energy functional within phase-field models to address mass conservation issues. The redefined functional helps avoid nonphysical bulk diffusion and ensures a proper energy balance, thereby improving the model's accuracy in simulating phenomena where mass loss is critical, such as in materials science and phase transitions.
Efficient Scalable Simulation of Burden Flow Using a Non-spherical Particle: DEM Approach
BHM Berg- und Hüttenmännische Monatshefte (01/11/2013)Goniva, Christoph; Kloss, Christoph; Feilmayr, Christoph; Pirker, Stefan
This study presents a numerical model for simulating burden flow in blast furnaces, integrating Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM). The model emphasizes non-spherical particle shapes to closely replicate physical phenomena. This approach enhances the accuracy of simulations, providing valuable insights into the complex behaviors of granular materials in industrial processes.
A resolved two-way coupled CFD/6-DOF approach for predicting embolus transport and the embolus-trapping efficiency of IVC filters
Biomechanics and Modeling in Mechanobiology (01/06/2017)Aycock, Kenneth I.; Campbell, Robert L.; Manning, Keefe B.; Craven, Brent A.
The paper introduces a resolved two-way coupled Computational Fluid Dynamics (CFD) and Six Degrees of Freedom (6-DOF) approach for simulating the movement of emboli in the cardiovascular system and evaluating the trapping efficiency of Inferior Vena Cava (IVC) filters. IVC filters are designed to prevent the passage of emboli from the lower extremities to the heart and lungs, which can cause severe complications such as pulmonary embolism. This model aims to enhance the understanding and effectiveness of IVC filters by providing a detailed simulation that includes both fluid dynamics and the filter's physical response to emboli.
Transfer chutes: Predicting dust emissions by multiphase CFD and coupled DEM-CFD simulations
Bulk Solids Handling (01/01/2014)Goniva, Christoph; Kloss, Christoph; Chen, X.; Donohue, Tim; Katterfeld, André
Dust emission is one of the main problems in the operation of transfer chutes. The design of the transfer chute heavily influences any potential dust generation. Although this influence is well known, much more attention is given to active dust suppression via water spray systems, the exhaustion of the dust polluted air or the use of electrostatic filters rather than the design optimization of the transfer chute.
Simulation of wear and dust emission at a transfer chute
Cement International (01/05/2012)Kloss, Christoph; Goniva, Christoph; Katterfeld, André
In this contribution the dust emission and wear at a transfer chute is investigated by means of numerical simulations using a coupled Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). This flexible and detailed modelling approach helps to obtain an insight into dust generation and propagation as well as wear in industrial plants. The first part of this paper deals with the optimization of a transfer chute in terms of dust emission and the second part deals with local wear prediction.
A comprehensive frictional-kinetic model for gas–particle flows: Analysis of fluidized and moving bed regimes
Chemical Engineering Science (01/10/2012)Schneiderbauer, Simon; Aigner, Andreas; Pirker, Stefan
This study introduces a comprehensive frictional-kinetic model for gas–particle flows, treating both gas and particles as continua. The model integrates the kinetic theory of granular flows to account for kinetic-collisional stresses and employs inertial number-dependent rheology alongside dilation laws to represent frictional stresses. This approach effectively captures the transition between collisional and frictional regimes in dense granular flows, enhancing the accuracy of simulations in various engineering applications.
Experimental and numerical investigation of sloshing resonance phenomena in a spring-mounted rectangular tank
Chemical Engineering Science (01/01/2012)Pirker, S.; Aigner, A.; Wimmer, G.
Inspired by the dynamics observed in a steelmaking converter, this study examines liquid sloshing using a simplified experimental setup with a rectangular tank mounted on a spring-controlled seesaw. The experiments addressed various scenarios: a collapsing water column and gas injection-induced sloshing in both fixed and spring-mounted tanks. In spring-mounted configurations, the study highlighted that when the mechanical eigenfrequency of the suspension system aligns with the wave frequencies, a resonance occurs, leading to beat-like energy transfers that periodically increase and decrease the load on the system. These findings are supported by analytical evaluations and 3D multiphase flow simulations, which generally align with the experimental results but show artificially damped sloshing motions.
Fluid and particle coarsening of drag force for discrete-parcel approach
Chemical Engineering Science (01/11/2016)Ozel, Ali; Kolehmainen, Jari; Radl, Stefan; Sundaresan, Sankaran
Fine-grid Euler–Lagrange simulations were performed to study gas-fluidization of uniformly sized particles in three-dimensional periodic domains. These simulations were coarse-grained to derive filter size dependent corrections for drag laws in Euler–Euler (EE) and Multi-Phase Particle-in-Cell (MP-PIC) models. The corrections mostly stem from fluid cell coarsening rather than particle phase coarsening. This discovery indicates that drag models developed for coarse EE simulations are also applicable to MP-PIC simulations, facilitating mutual drag correction applicability between these simulation types.
Handling contact points in reactive CFD simulations of heterogeneous catalytic fixed bed reactors
Chemical Engineering Science (01/02/2016)Rebughini, Stefano; Cuoci, Alberto; Maestri, Matteo
This study focuses on the crucial role of mesh generation in Computational Fluid Dynamics (CFD) simulations, particularly for handling contact points in random packed beds of spheres. It systematically investigates the treatment of contact points in reactive gas-solid packed bed simulations, building on prior research on radial heat transfer and pressure drop. The study extends and evaluates the bridge method to surface reactions, beginning with an analysis of a regular bed of spheres under laminar conditions (Re~80). This setup allows for precise meshing at contact points, enabling explicit comparisons between meshes with and without bridges. From these comparisons, guidelines are developed and tested on the meshing of a random packed bed reactor, establishing a meshing protocol that ensures accurate descriptions of surface reactivity, pressure drops, and heat transfer in packed bed reactors.
Color-PTV measurement and CFD-DEM simulation of the dynamics of poly-disperse particle systems in a pseudo-2D fluidized bed
Chemical Engineering Science (01/04/2018)Jiang, Zhaochen; Hagemeier, Thomas; Bück, Andreas; Tsotsas, Evangelos
In this study, a novel color particle tracking velocimetry (PTV) method is developed for pseudo-2D fluidized beds, utilizing the Voronoi tracking algorithm combined with the relaxation probability tracking algorithm. This method is designed to measure velocities of differently-sized, color-marked particles. Its effectiveness is verified through synthetic images from CFD-DEM simulations, assessing factors like segmentation bias, segmentation ratio, recovery ratio, and error ratio. The color-PTV method demonstrated strong performance in tracking a large number of distinct particles in poly-disperse systems. Additionally, comparisons of experimental results with CFD-DEM simulations using various drag models revealed that simulations incorporating corrections for particle size dispersity showed markedly better alignment with experimental data in terms of mixing index, time-averaged volumetric particle flux, and velocity and granular temperature distributions among particles.
Accuracy and comparison of standard k-ϵ with two variants of k-ω turbulence models in fluvial applications
Engineering Applications of Computational Fluid Mechanics (01/01/2018)Farhadi, Alireza; Mayrhofer, Arno; Tritthart, Michael; Glas, Martin; Habersack, Helmut
The paper discusses a new parametric method for aerodynamic optimization of high-speed trains, specifically focusing on reducing train wind effects. It employs a multi-objective particle swarm optimization algorithm to manage various design variables, such as the train’s cross-section, which significantly impacts its aerodynamic performance. The study also introduces a parametrization technique using the NURBS method for more flexible train body profiling. This method allows for a detailed analysis of how changes in the train's design affect its aerodynamics, aiming to optimize the streamlined shape for reduced wind resistance and improved efficiency.
A comprehensive comparison of Two-Fluid Model, Discrete Element Method and experiments for the simulation of single- and multiple-spout fluidized beds
Chemical Engineering Science (01/03/2023)Esgandari, Behrad; Rauchenzauner, Stefanie; Goniva, Christoph; Kieckhefen, Paul; Schneiderbauer, Simon
In this study, we use a two-fluid model (TFM) and a computational fluid dynamics-discrete element method (CFD-DEM) approach to analyze the time-averaged hydrodynamics of single- and multiple-spout fluidized beds. The simulations were validated using experimental data from van Buijtenen et al. (2011), incorporating four different interphase drag correlations. The TFM approach includes detailed kinetic theory modeling of granular flows with enhanced particle–wall interactions and an innovative modification of the -rheology to incorporate rolling friction effects. In contrast, the CFD-DEM method integrates rolling friction through an additional torque component. Both methods showed strong agreement in predicting key parameters such as volume fraction, particle velocities, fluxes, and granular temperature, demonstrating the robustness and accuracy of the models in simulating complex fluidized bed dynamics.
Simulation of Flow in Multi-Scale Porous Media Using the Lattice Boltzmann Method on Quadtree Grids
Communications in Computational Physics (01/04/2016)Zhang, Lei; Kang, Qinjun; Chen, Li; Yao, Jun
The unified lattice Boltzmann model is enhanced by integrating with quadtree grids to simulate fluid flow in porous media. This model supports multi-scale flow simulation in complex systems and leverages quadtree grids for high-resolution approximation and flexible grid density control. This efficient combination is applied to calculate permeability in various systems, including fractured media, Voronoi tessellations, and computationally generated fractured shale structures. Comparisons with traditional models demonstrate its accuracy and efficiency. Specifically, it effectively distinguishes between matrix and fracture flows in shale, highlighting its utility in analyzing multi-scale porous media.
Efficient implementation of superquadric particles in Discrete Element Method within an open-source framework
Computational Particle Mechanics (01/01/2017)Podlozhnyuk, Alexander; Pirker, Stefan; Kloss, Christoph
The article discusses the development and optimization of particle shape representation in DEM simulations. Traditional DEM models primarily use spherical particles due to their simplicity and computational efficiency. However, real-world applications often involve non-spherical particles, necessitating more complex modeling approaches. This paper introduces superquadric particles, which provide a more accurate representation of various particle shapes in DEM simulations, thus enhancing the model's applicability to real-world scenarios such as industrial processing and materials handling.
Onset of sediment transport in mono- and bidisperse beds under turbulent shear flow
Computational Particle Mechanics (01/04/2018)Seil, Philippe; Pirker, Stefan; Lichtenegger, Thomas
The paper discusses the development and optimization of particle shape representation in DEM simulations. Traditional DEM models primarily use spherical particles due to their simplicity and computational efficiency. However, real-world applications often involve non-spherical particles, necessitating more complex modeling approaches. This paper introduces superquadric particles, which provide a more accurate representation of various particle shapes in DEM simulations, thus enhancing the model's applicability to real-world scenarios such as industrial processing and materials handling.
Calibration of particle interactions for discrete element modeling of powder flow
Computational Particle Mechanics (01/08/2024)Fazzino, Mike; Habiba, Ummay; Kuna, Lukasz; Nakhmanson, Serge; Hebert, Rainer J.
An experiment using an ASTM B213 standard Hall Flowmeter Funnel was conducted on Ti 6–4 powder particles and simulated via discrete element method in LIGGGHTS. Particle interactions were modeled with a modified Johnson–Kendall–Roberts theory incorporating adhesion based on surface free energy. The simulations used actual particle size distribution data and adjustable parameters like cohesion energy density, restitution coefficient, and dynamic friction were fine-tuned to resemble the experimental particle pile shape. Simulated geometrical properties of the powder pile were measured and compared to experimental outcomes. Local particle size variations within the pile were analyzed, revealing a segregation with larger particles at the top, similar to the Brazil nut effect.
Closure Development for Multi-Scale Fluidized Bed Reactor Models: A Case Study
Computer Aided Chemical Engineering (04/07/2018)Radl, Stefan; Municchi, Federico; Cloete, Schalk; Cloete, Henrik; Andersson, Stefan; Morgado, Joana Francisco; Gurker, Thomas; Quinta-Ferreira, Rosa; Kloss, Christoph; Goniva, Christoph; Amini, Shahriar
Chemical looping reforming (CLR) processes highlight significant challenges in chemical engineering, particularly in managing transport limitations. The "NanoSim" project has developed a computational platform to address a wide range of these complexities, including diffusion in solids and nanometer-scale pores, heat and mass transfer between particles and gases, meso-scale clustering, and large-scale dispersion within a reactor. The study reveals that even at the particle scale, considerable uncertainties arise due to the spontaneous formation of meso-scale structures, which affect flow, transport, and reactions. These findings underscore the importance of accounting for these heterogeneities in CLR models to accurately predict reaction rates in industrial-scale reactors.
CFD-DEM simulation of a fluidized bed crystallization reactor
Computer Aided Chemical Engineering (10/06/2015)Kerst, Kristin; Medeiros De Souza, Luis; Bartz, Antje; Seidel-Morgenstern, Andreas; Janiga, Gábor
In the present study, a fluidization process in a fluidized bed crystallizer is examined using multiphase CFD-DEM (CFD: Computational Fluid Dynamics; DEM: Discrete Element Method) simulations. The simulations were carried out using the coupled open source software CFDEMcoupling. After validating the simulation results with first experimental measurements, have been used for process understanding and improvement. In particular, regions with complex flow features but important for process outcome have been identified within the crystallizer. Moreover the simulations delivered valuable information that are difficult or even impossible to measure experimentally with sufficient accuracy.
Combining Open Source and Easy Access in the field of DEM and coupled CFD-DEM: LIGGGHTS®, CFDEM® coupling and CFDEM® workbench
Computer Aided Chemical Engineering (04/07/2018)Hager, Alice; Kloss, Christoph; Goniva, Christoph
The Discrete Element Method (DEM) and its integration with Computational Fluid Dynamics (CFD-DEM) are crucial for designing and optimizing particle processes in various industries. The open-source platforms, CFDEM®coupling and LIGGGHTS®, offer sophisticated simulation capabilities but can be complex to install. The commercial GUI, CFDEM®workbench, simplifies access by combining the advantages of open-source software with an easy setup process. This tool enables broader application of DEM and CFD-DEM modeling in industries like steel, pharmaceuticals, and food production, enhancing the practical utility of these advanced simulation technologies.
Turbulence Budgets in Buoyancy-affected Vertical Backward-facing Step Flow at Low Prandtl Number
Flow, Turbulence and Combustion (01/12/2017)Niemann, Martin; Fröhlich, Jochen
This study uses Direct Numerical Simulation to examine the effect of buoyancy on vertical flow over a backward-facing step, particularly with low Prandtl number liquid sodium under mixed convection. It finds that buoyancy reduces recirculation, enhancing heat transfer while varying turbulence effects—decreasing it under moderate conditions and increasing it at high Richardson numbers. The study also analyzes budgets for turbulent kinetic energy, Reynolds shear stress, and heat flux components, highlighting the influence of temperature-pressure gradient correlations. This research aids in understanding liquid metal flows and improving turbulence models for such conditions.
Investigation of wall bounded flows using SPH and the unified semi-analytical wall boundary conditions
Computer Physics Communications (01/11/2013)Mayrhofer, Arno; Rogers, Benedict D.; Violeau, Damien; Ferrand, Martin
This paper examines semi-analytical wall boundary conditions in smoothed particle hydrodynamics (SPH) for fluid flows, focusing on energy conservation and the skew-adjoint property. It reveals that exact energy conservation holds only in continuous SPH, with the discrete form approximating this, resulting in numerical "turbulence." This issue is addressed using a volume diffusion term akin to an approximate Riemann solver. Additionally, enhancements include variable driving force management in periodic flows and generalized Robin-type wall boundary conditions. Numerical experiments validate these advancements, showing significant error reduction and improved handling of free-surface flows, particularly in preventing surface detachment and optimizing interactions at walls.
Highly efficient spatial data filtering in parallel using the opensource library CPPPO
Computer Physics Communications (01/10/2016)Municchi, Federico; Goniva, Christoph; Radl, Stefan
CPPPO is a library developed to facilitate "scale bridging" in multi-scale approaches, integrating parallel data processing routines for both structured and unstructured Eulerian meshes, and Lagrangian data sets. It enables on-the-fly data processing, eliminating the need for storing individual simulation snapshots. Compatible with OpenFOAM®, CPPPO can also interface with other software. The library introduces an advanced parallel data filtering technique that exhibits super-linear scaling on multi-core clusters. Additionally, it offers guidelines for selecting the most effective Eulerian cell selection algorithm based on CPU core count, with demonstrated effectiveness in heat and mass transfer simulations involving dense particle beds.
Heat transfer rates in sheared beds of inertial particles at high Biot numbers
Granular Matter (01/02/2017)Forgber, Thomas; Mohan, Bhageshvar; Kloss, Christoph; Radl, Stefan
This study investigates heat conduction through sheared granular materials using the ParScale solver and LIGGGHTS discrete element method. Heat transfer to the ambient fluid is modeled with a fixed coefficient, focusing on Biot and Peclet numbers as key parameters for describing heat flux. An analytical solution is provided for calculating mean particle temperature profiles, leading to a continuum model for heat flux developed through extensive simulations. Results show that low Biot numbers align with a simple model assuming uniform particle temperature, whereas higher numbers require accounting for internal temperature gradients to accurately predict heat transfer rates.
Comparing open-source DEM frameworks for simulations of common bulk processes
Computer Physics Communications (01/03/2024)Dosta, M.; Andre, D.; Angelidakis, V.; Caulk, R.A.; Celigueta, M.A.; Chareyre, B.; Dietiker, J.-F.; Girardot, J.; Govender, N.; Hubert, C.; Kobyłka, R.; Moura, A.F.; Skorych, V.; Weatherley, D.K.; Weinhart, T.
This study conducts a comparative analysis of nine widely-used, open-source Discrete Element Method (DEM) software frameworks for simulating granular materials. Each framework utilizes explicit time integration, involving contact detection, interaction calculations, and motion equation integration. Significant differences among them include contact models, particle shapes, data analysis methods, data structures, software architecture, parallelization techniques, and user interfaces. The benchmarks, using common bulk processes like silo emptying, drum mixing, and particle impact, employed standard features like spherical particles and the Hertz-Mindlin dry contact model. Scripts for these benchmarks are also provided, facilitating reproducibility and further testing.
A semi-implicit immersed boundary method and its application to viscous mixing
Computers & Chemical Engineering (14/12/2015)Blais, Bruno; Lassaigne, Manon; Goniva, Christoph; Fradette, Louis; Bertrand, François
This study addresses challenges in single-phase mixing CFD simulations caused by complex rotating geometries. A parallel semi-implicit immersed boundary method developed in Open∇FOAM for unstructured meshes is introduced. Initially validated through academic test cases, the method was applied to single-phase mixing in both baffled and unbaffled stirred tanks with a pitched blade impeller. The simulation results were benchmarked against experimental data and outcomes from single rotating frame and sliding mesh techniques. The new method demonstrated accuracy comparable to these traditional techniques in predicting flow patterns and torque values, with added ease of application to complex systems featuring multiple overlapping impellers.
An efficient multiple marker front-capturing method for two-phase flows
Computers & Fluids (01/06/2012)Kwakkel, Marcel; Breugem, Wim-Paul; Boersma, Bendiks Jan
This study introduces a novel approach for simulating fluid-particle interactions by integrating the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD). The authors employ an immersed boundary method to represent particles within the fluid grid, allowing for accurate modeling of complex interactions. Validation against experimental data demonstrates the model's effectiveness in predicting particle behavior in fluid flows, offering a valuable tool for engineering applications involving particulate systems.
DNS and LES of 3-D wall-bounded turbulence using Smoothed Particle Hydrodynamics
Computers & Fluids (01/07/2015)Mayrhofer, A.; Laurence, D.; Rogers, B.D.; Violeau, D.
Smoothed Particle Hydrodynamics (SPH) has expanded its application to include real-world engineering scenarios, particularly in simulating turbulent three-dimensional flows. This paper highlights a significant gap in the investigation of such flows, as most SPH studies focus on the decay of isotropic turbulence without solid wall influences. The study conducts two sets of SPH simulations on turbulent channel flows. The first, a quasi-direct numerical simulation (DNS) in a reduced-size channel, tests SPH's capability as a Navier–Stokes solver without turbulence models, successfully reproducing turbulent statistics except near the wall. The second set, a large eddy simulation (LES) in a standard size channel, fails to accurately predict turbulent statistics, with failures linked to inadequate velocity-pressure interaction handling by SPH’s collocated and large stencil discretization.
Numerical and experimental analysis of the extraction mechanism of an anchor plate embedded in saturated sand
Computers and Geotechnics (01/07/2019)Kanitz, M.; Hager, A.; Grabe, J.; Goniva, C.
Floating offshore structures often use submerged anchor plates for foundational support, requiring understanding of their extraction resistance under various conditions. Throughout their lifecycle, these foundations face complex loading from waves, tidal currents, and wind. Notably, when extracting these anchors at lifecycle’s end, their resistance significantly exceeds the combined forces of self-weight, hydrostatic, and earth pressures due to a vacuum effect as the anchor moves and increases the volume underneath, drawing in pore water. An experimental model-scale study measured pore pressures and soil movements using particle image velocimetry (PIV), exploring different extraction velocities. Additionally, numerical simulations using unresolved coupled CFD-DEM methods validated these experimental findings, enhancing understanding of anchor extraction dynamics.
DNS of Turbulent Bubbly Downflow with a Coupled Level-Set/Volume-of-Fluid Method
Direct and Large-Eddy Simulation IX (01/01/2015)Kwakkel, M.; Breugem, W. -P.; Boersma, B. J.
Turbulent flows containing bubbles or droplets play a critical role in both industrial applications and natural processes, such as in bubble column reactors, spray combustion systems, and rain clouds. Understanding the interactions between these bubbles or droplets and the turbulent flow around them is challenging, especially when these particles are of finite size relative to the Kolmogorov scale and are present in concentrations beyond dilute conditions. The complexity of these interactions remains a significant area of research due to its implications on the efficiency and effectiveness of various systems involving multiphase flows.
Buoyancy Effects on Turbulent Heat Transfer Behind a Backward-Facing Step in Liquid Metal Flow
Direct and Large-Eddy Simulation X (08/10/2018)Niemann, M.; Fröhlich, Jochen
Heat transfer is one the most important technical applications in fluid mechanics. Heat transfer behind sudden changes of the cross section such as a backward-facing step flow is particularly important in many devices such as the in- and outflow of thermal storage containers, collectors of power conversion systems, as well as highly heat loaded surfaces like those in concentrated solar power (CSP) plants, to name but a few examples.
CFD–DEM study of residence time, droplet deposition, and collision velocity for a binary particle mixture in a Wurster fluidized bed coater
Drying Technology (01/04/2018)Jiang, Zhaochen; Bück, Andreas; Tsotsas, Evangelos
The article delves into optimizing the drying process of pharmaceutical powders using fluidized bed drying technology. It focuses on examining various parameters such as air flow rate, temperature, and particle characteristics to enhance the efficiency and uniformity of the drying process. This study is critical for improving product quality and reducing production costs in the pharmaceutical industry, where moisture content and particle integrity are crucial.
Influence of various DEM shape representation methods on packing and shearing of granular assemblies
Granular Matter (01/05/2021)Soltanbeigi, Behzad; Podlozhnyuk, Alexander; Kloss, Christoph; Pirker, Stefan; Ooi, Jin Y.; Papanicolopulos, Stefanos-Aldo
This paper examines how different shape representation methods influence the bulk response of granular assemblies in Discrete Element Method simulations, focusing on angle-of-repose and direct-shear tests. It considers three rolling resistance models for spherical particles and uses superquadrics and multi-spheres to model non-spherical particles like cuboids and cylinders. The study presents detailed results on how shape affects granular behavior, including comparisons of various methods. Findings from angle-of-repose tests indicate that rolling friction models effectively capture the avalanching characteristics of cube-like and cylindrical particles. Direct-shear test results highlight that only the elasto-plastic rolling resistance model accurately predicts shear strength and dilative response, although not porosity, of non-spherical particles. This research helps pinpoint optimal shape-description parameters for different representation methods.
A semi-analytical model for the effective thermal conductivity of a multi-component polydisperse granular bed
Granular Matter (01/11/2017)Martis, Joel; Annabattula, Ratna Kumar
A theoretical model to predict the effective thermal conductivity of a multi-component polydisperse granular bed is presented. A simple energy balance analysis is used to arrive at an approximate analytical expression for the effective thermal conductivity. Simulation of heat transfer in a granular bed is carried out using an open source Discrete Element Method (DEM) package called LIGGGHTS. The derived analytical expressions for the effective thermal conductivity compares well with the results obtained from DEM simulations for granular beds comprising of different components with different sizes.
A viscoelastic bonded particle model to predict rheology and mechanical properties of hydrogel spheres
Granular Matter (01/07/2024)Mascara, Michael; Shakya, Chandan; Radl, Stefan; Mayrhofer, Arno; Kloss, Christoph
The study introduces a numerical simulation tool based on the Discrete Element Method tailored for predicting the behavior of hydrogel spheres, extensively used in various sectors due to their adaptable mechanical properties. Initially, the model's accuracy is assessed through an oscillatory compression test on a single hydrogel, achieving a close match with experimental rheological properties; the relative errors for the normal modified storage and loss moduli (E’ and E”) are about 3% and 11%, respectively. This approach, utilizing bonded particles and a viscoelastic constitutive relation, is validated further with a particle-particle compression test, showing promising alignment with experimental contact forces. This model's adaptability makes it suitable for a broad range of applications.
Detection and Visualization of Splat and Antisplat Events in Turbulent Flows
IEEE Transactions on Visualization and Computer Graphics (01/11/2020)Nsonga, Baldwin; Niemann, Martin; Fröhlich, Jochen; Staib, Joachim; Gumhold, Stefan; Scheuermann, Gerik
The study introduces the first Lagrangian method for identifying splat and antisplat events in three-dimensional turbulent flows, where splats occur when fluid impinges on a surface, transferring energy from normal to tangential velocity components, and antisplats represent the reverse. This method employs strain tensors on flow-embedded flat surfaces to detect these events across various scales. Validated using artificial flow fields, the method was applied to analyze turbulent flow over a backward-facing step from direct numerical simulations. Results confirm the method's efficacy and reliability in identifying these events in complex flows, marking it as a valuable tool for analyzing turbulent flow dynamics.
Extended CFD–DEM for free‐surface flow with multi‐size granules
International Journal for Numerical and Analytical Methods in Geomechanics (01/01/2016)Jing, L.; Kwok, C. Y.; Leung, Y. F.; Sobral, Y. D.
The study enhances CFD-DEM modeling with the Volume of Fluid (VOF) method to simulate free-surface flows, integrating fluid dynamics on coarse grids with particle dynamics. This approach uses an advection equation to manage liquid phase fraction and enables volume replacement between fluid and particles. A novel "porous sphere" technique allows larger particle use without losing fluid grid resolution. Validations across scenarios like dam breaks and particle sedimentation confirm the effectiveness of the new solver, cfdemSolverVOF, even with a reduced size ratio between fluid cells and particle diameter, enhancing its suitability for dynamic geotechnical applications with diverse particle sizes.
Buoyancy-affected backward-facing step flow with heat transfer at low Prandtl number
International Journal of Heat and Mass Transfer (01/10/2016)Niemann, Martin; Fröhlich, Jochen
This paper explores turbulent upward flow of liquid metal in a vertical channel with a heated backward-facing step, pertinent to solar power plants. Direct numerical simulations assess the buoyancy effects by comparing scenarios with and without the buoyancy term, featuring a Richardson number of 0.338. The results show that buoyancy significantly alters the flow, reducing recirculation and enhancing heat transfer at the heated wall due to increased temperature advection. Detailed analysis of turbulent heat fluxes demonstrates how buoyancy modifies flow conditions. These insights help improve the physical understanding and modeling of turbulent heat transfer at low Prandtl numbers.
Direct numerical simulation of turbulent bubbly down flow using an efficient CLSVOF method
International Journal of Multiphase Flow (01/02/2021)Nemati, Hassan; Breugem, Wim-Paul; Kwakkel, Marcel; Jan Boersma, Bendiks
This study uses Direct Numerical Simulations (DNS) to explore how bubbles affect turbulence in downward-flowing vertical channels. With a Reynolds number of 180, simulations are carried out for two void fractions, analyzing three bubble sizes using the Coupled Level-Set/Volume-of-Fluid (CLSVOF) method. Efficiency improvements are made with a fast pressure-correction method, allowing FFT-based solutions. Validation shows excellent accuracy, with a significant speedup of 22 times by the new solver. Results indicate bubble accumulation in the channel core, altering the mean velocity profile and reducing velocity fluctuations near the walls, while enhancing turbulence in the core. Larger bubbles increase dissipation, amplifying turbulent kinetic energy centrally.
Investigating mixing and segregation using discrete element modelling (DEM) in the Freeman FT4 rheometer
International Journal of Pharmaceutics (01/11/2016)Yan, Zilin; Wilkinson, Sam K.; Stitt, Edmund H.; Marigo, Michele
The study utilizes the Discrete Element Method (DEM) to examine mixing and segregation dynamics in a Freeman FT4 powder rheometer with binary particle mixtures, focusing on varying particle size ratios and volume fractions. It finds that larger particle sizes or greater volume fractions of large particles accelerate segregation through a sifting mechanism, enhanced by higher particle velocities. Segregation intensifies radially from the center to the outer layer. Additionally, the study notes that segregation and mixing energies are influenced by frictional parameters. The FT4 rheometer's potential is highlighted for evaluating particulate materials' segregation tendencies by measuring flow energy gradients post-mixing cycles, aiding in optimizing blending operations in industrial settings.
Review and future options for computer modelling in the sugar industry
International Sugar Journal (01/10/2014)Plaza, Floren; Kent, G.A.; Rackemann, Darryn; Stephens, Darrin
This paper provides a review of computer modeling applications in the sugar industry over the past 25 years, highlighting both successes and challenges. It notes that while advancements in hardware and software have enhanced modeling capabilities, certain processes like cane cleaning, billet preparation, and sugar drying have seen limited improvement due to the computational intensity required to model numerous particle interactions. Despite these challenges, progress has been made in understanding these complex systems. The paper suggests employing robust commercial software with customizable subroutines or leveraging open-source software capable of utilizing large parallel computing resources to overcome computational barriers. It discusses software options that could potentially enhance efficiency and design within the industry.
Thermo-hydraulic flow in a sudden expansion
IOP Conference Series: Materials Science and Engineering (01/07/2017)Jaeger, W; Schumm, T; Niemann, M; Hering, W; Stieglitz, R; Magagnato, F; Frohnapfel, B; Fröhlich, J
The article explores enhancements in DEM simulations by incorporating superquadric particles. These particles offer a more realistic representation of varied particle shapes, which is crucial for applications like materials processing and handling. This advancement allows for the simulation of complex particle interactions more accurately than traditional spherical models.
Transition between free, mixed and forced convection
IOP Conference Series: Materials Science and Engineering (01/07/2017)Jaeger, W; Trimborn, F; Niemann, M; Saini, V; Hering, W; Stieglitz, R; Pritz, B; Fröhlich, J; Gabi, M
The study investigates optimal conditions for producing charcoal from coconut shells, focusing on temperature and residence time's effects on charcoal yield. It includes a detailed experimental setup using a pyrolysis reactor and discusses the thermal conversion of the shells, highlighting the relationship between process parameters and the efficiency of charcoal production.
Direct Minimization of the least-squares spectral element functional – Part I: Direct solver
Journal of Computational Physics (01/02/2008)Hoitinga, Wijnand; De Groot, Roel; Kwakkel, Marcel; Gerritsma, Marc
The paper presents a method for solving the Helmholtz equation using spectral element methods. The authors propose a direct minimization approach to obtain the least-squares solution, aiming to improve computational efficiency and accuracy in solving this fundamental equation in physics and engineering.
Extension of a CLSVOF method for droplet-laden flows with a coalescence/breakup model
Journal of Computational Physics (01/11/2013)Kwakkel, Marcel; Breugem, Wim-Paul; Boersma, Bendiks Jan
The CLSVOF method for droplet-laden flows now includes a model for droplet coalescence and breakup, enhancing its realism. This method uses unique marker functions for each droplet to avoid numerical coalescence seen in traditional methods. Coalescence is determined by a film drainage model, which activates when contact time exceeds a set threshold, merging droplet markers. Breakup is modeled by splitting these markers. Validated by simulations at various Weber numbers
Development of an unresolved CFD–DEM model for the flow of viscous suspensions and its application to solid–liquid mixing
Journal of Computational Physics (01/08/2016)Blais, Bruno; Lassaigne, Manon; Goniva, Christoph; Fradette, Louis; Bertrand, François
Viscous solid-liquid mixing, crucial in industries, is often studied in turbulent regimes, but challenges persist in laminar and transitional flows. This paper discusses using multiphase CFD to examine such mixings, especially the unresolved CFD-DEM method that combines fluid dynamics with discrete element modeling to simulate large quantities of particles accurately. This study extends the method to viscous flows, exploring various momentum coupling strategies and introducing a sub-grid viscosity model to maintain correct suspension rheology. The model is applied to a stirred tank with a pitched blade turbine, and validated both qualitatively and quantitatively against experimental data, demonstrating its effectiveness in predicting particle suspension behaviors.
Physical and scale-by-scale analysis of Rayleigh–Bénard convection
Journal of Fluid Mechanics (01/11/2015)Togni, Riccardo; Cimarelli, Andrea; De Angelis, Elisabetta
The article presents a novel approach to studying turbulent Rayleigh–Bénard convection (RBC) in a compound physical/scale space domain. It utilizes data from direct numerical simulations conducted in a laterally unbounded domain confined between two horizontal walls, exploring cases with a Prandtl number of 0.7 and Rayleigh numbers ranging from 1.7×10^5 to 1.0×10^7. This study offers insights into the dynamics and scale interactions within turbulent RBC, contributing valuable understanding to the field of fluid dynamics.
Resolved and subgrid dynamics of Rayleigh–Bénard convection
Journal of Fluid Mechanics (01/05/2019)Togni, Riccardo; Cimarelli, Andrea; De Angelis, Elisabetta
This work introduces a theoretical framework for analyzing thermally driven turbulence, extending classical equations to accommodate inhomogeneous and anisotropic flows. It utilizes scale-by-scale budget equations for velocity and temperature structure functions, identifying two critical scales that delineate quasi-homogeneous and inhomogeneity-dominated ranges. Applied to large-eddy simulation, it assesses filtering effects on Rayleigh–Bénard convection dynamics. Results indicate that classic eddy-viscosity models may be inadequate for large filter lengths, suggesting alternative subgrid closures are needed. This framework offers a valuable tool for evaluating subgrid-scale models in simulations of turbulent flows.
Effects of Contact Force Model and Size Distribution on Microsized Granular Packing
Journal of Manufacturing Science and Engineering (01/04/2014)Dou, Xin; Mao, Yijin; Zhang, Yuwen
The article discusses the importance of contact force models in the accurate simulation and understanding of mechanical systems where contact occurs, such as in manufacturing processes. The study analyzes different models for their effectiveness in predicting the behavior of systems at various scales, particularly focusing on the scalability and applicability of these models in real-world scenarios. This research is crucial for advancing precision in manufacturing techniques and improving the design and efficiency of mechanical assemblies and tools.
What are the microscopic events of colloidal membrane fouling?
Journal of Membrane Science (01/05/2018)Lohaus, J.; Perez, Y.M.; Wessling, M.
This study employs CFD-DEM simulations to analyze colloidal membrane fouling within a microfluidic system that simulates a porous microfiltration membrane. It focuses on how colloidal particles overcome energy barriers for adsorption and desorption, both between particles and with membrane surfaces. Key insights include the transition of particle interactions from the secondary to the primary minimum of the DLVO potential and the behaviors of adsorbed particles, such as re-entrainment or downstream gliding, often occurring in clusters. The pore geometry within the membrane notably influences fouling patterns. These findings lay groundwork for further exploration of the dynamics between hydrodynamic forces and surface energy effects in colloidal filtration.
Fully-resolved simulations of particle-laden viscoelastic fluids using an immersed boundary method
Journal of Non-Newtonian Fluid Mechanics (01/04/2019)Fernandes, C.; Faroughi, S.A.; Carneiro, O.S.; Nóbrega, J. Miguel; McKinley, G.H.
This study introduces a direct simulation code developed to analyze the dynamics of solid spheres in viscoelastic fluids, utilizing an open-source finite-volume solver enhanced by an immersed boundary method. This solver is designed to handle fully-resolved simulations and employs a log-conformation tensor to manage issues at high Weissenberg numbers effectively. Benchmark tests include sphere sedimentation in viscoelastic and Newtonian fluids, rotation in shear flows, and cross-stream migration in Poiseuille flow, with results validated against experimental and computational references. Additionally, the solver's accuracy in capturing phenomena like the Segré–Silberberg effect and shear-induced particle alignment was demonstrated, showing the influence of fluid rheology and confinement on particle dynamics.
Space and time behaviour of the temperature second-order structure function in Rayleigh-Bénard convection
Journal of Physics: Conference Series (01/04/2016)Togni, Riccardo; Cimarelli, Andrea; Lozano-Durán, Adrián; Angelis, Elisabetta De
The article discusses the flow structure of an under-expanded supersonic impinging (USI) jet, where the flow exits from the nozzle at a Mach number of 1 and impinges on a wall placed vertically above the nozzle. The study models the behavior and interactions at different distances, specifically focusing on a distance of five times the nozzle diameter (z/d = 5). This setup is used to observe the dynamic effects and flow patterns that result when the supersonic jet impacts the impingement surface, which is crucial for applications in aerospace and other industries requiring precise control of jet behaviors.
Modeling of wheel–soil interaction over rough terrain using the discrete element method
Journal of Terramechanics (01/10/2013)Smith, William; Peng, Huei
A numerical study utilizing the Discrete Element Method (DEM) examined the effects of rough terrain on the mobility and efficiency of small unmanned ground vehicles. The DEM simulations, validated against single-wheel test data involving straight-line motion and wheel-digging on flat soil, showed good qualitative agreement. In tests on 20 sinusoidal rough terrain profiles, mobility generally decreased, with drawbar pull dropping by up to 15% and driving torque increasing by up to 35% due to terrain-induced oscillations. The experiments used a slow speed and soft lunar regolith simulant, which minimized vertical accelerations and vehicle vibrations, thereby reducing performance impacts.
Simulation von Förderprozessen bei Vibrationsförderanlagen
Logistics Journal (01/10/2012)Dallinger, Niels; Risch, Thomas; Nendel, Klaus
The paper discusses the achievable conveying speeds of vibratory conveyors and their dependency on the motion function of the conveyor mechanism. It emphasizes the need for targeted simulation of these systems using the discrete element method (DEM), necessitating the application of geometrically networked conveyor replicas with practice-relevant motion functions to accurately model and optimize vibratory conveying processes.
Simulation der peristaltischen Förderung von Stückgütern als Schüttgut
Logistics Journal : referierte Veröffentlichungen (01/09/2014)Cao, Liu; Richter, Klaus; Richter, Christian; Katterfeld, André
The article introduces a novel conveying principle designed to resiliently handle and transport bulk package structures. This system utilizes a flexible composite surface made up of small-scale conveyor modules, which exhibit peristaltic properties to quickly resolve package jams and allow controlled handling of sub-quantities to achieve necessary throughput in material flow systems. This concept effectively combines principles of bulk and unit load conveying for transporting packages as bulk material. The basic functionality of the conveyor concept is validated through numerical simulations using the Discrete Element Method and multibody simulation.
Single Particle Growth, Fragmentation and Morphology Modelling: A DEM Approach
Macromolecular Reaction Engineering (01/12/2022)Soleimani, Afsaneh; Aigner, Andreas; Touloupidis, Vasileios
The paper discusses the synthesis and characterization of polyacrolein using radical polymerization methods. Optimal conditions for acrolein polymerization are achieved using I4 as an initiator at a ratio of 1:50 to the monomer, with a monomer concentration of 7.5 mol L^-1, a reaction temperature of 50 °C, and a duration of 6 hours. Under these conditions, the yield of polyacrolein can reach up to 93.76%. The polymers formed are further characterized to confirm their structure and properties, which is essential for their potential application in various industrial fields.
Stochastic simulation of the Uplift process for the Irish Electricity Market
Mathematics-in-Industry Case Studies (01/09/2010)Jabłońska-Sabuka, Matylda; Mayrhofer, Arno; Gleeson, James
In the Irish electricity market participants declare their true marginal costs and therefore the Shadow Price alone does not guarantee that generators will recover their fixed running costs. The so-called uplift complements the price and ensures that the generators recover their total costs. The aim of this paper is to review purely stochastic features of the uplift and make an attempt to simulate a new process reconstructing the original data characteristics. We propose two alternative algorithms basing on the uplift wait-jump structure as well as daily and annual seasonality. Presented results show that this kind of reconstruction is possible up to a quantitatively comparable degree.
Direct Numerical Simulation of turbulent heat transfer behind a backward‐facing step at low Prandtl number
PAMM (01/12/2014)Niemann, Martin; Fröhlich, Jochen
The paper presents Direct Numerical Simulations of the turbulent flow of a low Prandtl number fluid over a backward‐facing step with heat transfer. The backward‐facing step flow is investigated as a generic configuration for sudden changes in cross section. Several simulations are reported: for isothermal conditions, for heat transfer with the Prandtl number of air, and for heat transfer with the Prandtl number of liquid sodium. The simulation for air is compared to results from literature. The differences induced by reduction of the Prandtl number are then assessed by comparison of the two cases. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of isotropic and anisotropic subgrid scale models in Large Eddy Simulations of a backward‐facing step and square duct flow
PAMM (01/10/2016)Temme, Nils; Niemann, Martin; Fröhlich, Jochen
The present paper employs the anisotropic explicit algebraic subgrid‐stress model (EASM), proposed by Marstorp et al., developed in the spirit of an earlier explicit algebraic RANS‐model for statistical closures. The EASM in its elementary, computationally efficient non‐dynamic version is used for Large Eddy Simulation of three‐dimensional flows over a backward‐facing step at a bulk Reynolds number of 4805 and a square duct at 2205. Its performance is assessed by comparison with experimental data and an own Direct Numerical Simulation. Furthermore, a set of eddy‐viscosity models, including the recent σ‐model, is employed for comparison. Various statistical quantities are evaluated to assess the respective performance of the different models showing, that the anisotropic EASM compares favorably to the other models.
Heated vertical duct flow of liquid metal with and without expansion
PAMM (01/12/2017)Niemann, Martin; Saini, Vishal; Fröhlich, Jochen
The effects of buoyancy on vertical duct flows with one heated side wall are investigated by means of Direct Numerical Simulations. In particular, the flow through square ducts and behind the expansion of a backward‐facing step with side walls are presented for the forced and mixed convection regime. These configurations allow studying the interaction of buoyancy forces with secondary flow of second kind in the square duct and with the shear layer and recirculation zone in case of the expansion. In both configurations, buoyancy substantially alters the mean flow field, the turbulent stresses, and the heat transfer compared to the corresponding forced convection cases.
A Modified Statistical Interparticle Collision Model For Colliding Particle Clouds
PAMM (26/02/2009)Kloss, C.; Pirker, S.
In this paper, a modified stochastical interparticle collision model is discussed and valdiated. A channel flow with a constriction serves as a test case. The simulation of the thereby colliding particle strands clearly shows that without the collision sub–model, the simulation with the standard Lagrangian model yields unreasonable results. After adding the stochastical collision sub–model, the Lagrangian model is able to describe the flow situation if the mass load is not too high.
Influence of rolling friction on single spout fluidized bed simulation
Particuology (01/10/2012)Goniva, Christoph; Kloss, Christoph; Deen, Niels G.; Kuipers, Johannes A.M.; Pirker, Stefan
This study introduces a novel approach to simulate the behavior of dense particle suspensions in fluid flows. By integrating the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD), the model effectively captures particle-particle and particle-fluid interactions. Validation against experimental data demonstrates its accuracy in predicting flow patterns and particle distribution, offering a valuable tool for analyzing complex multiphase flows in engineering applications.
Predictions of the P1 approximation for radiative heat transfer in heterogeneous granular media
Particuology (01/11/2023)Mačak, Jelena; Goniva, Christoph; Radl, Stefan
The P1 approximation, a simplified model for thermal radiation, is integrated into a combined CFD-DEM framework to enhance computational efficiency while handling dependent scattering and coarse-graining effects. Analysis using analytical solutions shows good agreement for steady-state and transient behaviors in size-disperse systems, though heat flux predictions exhibit unphysical oscillations due to temperature discrepancies at sharp changes in solid fraction. To address this, two solutions—smoothing radiative properties and introducing pseudo-scattering—are proposed. The framework supports extensive coarse-graining, tested up to a million times the particle size. Comparisons with experimental data from a pebbled bed in vacuum and nitrogen environments show that the model closely replicates observed trends, maintaining a relative temperature error under 10%.
Discrete particle simulation of radial segregation in horizontally rotating drum: Effects of drum-length and non-rotating end-plates
Physica A: Statistical Mechanics and its Applications (01/10/2012)Chand, Ram; Khaskheli, Murad Ali; Qadir, Abdul; Ge, Baoliang; Shi, Qingfan
DEM simulations explore the radial segregation of two different-sized grains in a horizontal rotating drum, focusing on the impact of drum length and grain-end-plate friction. Findings reveal that longer drums exhibit higher segregation ratios, with end-plate friction having minimal impact. Conversely, in shorter drums, segregation is slow or negligible, but reducing end-plate friction enhances segregation. Increasing friction beyond inter-grain and grain-wall friction decreases segregation in longer drums and promotes mixing in shorter ones. This behavior is attributed to diffusion caused by shearing strain from rougher end-plates, which raises granular temperature and leads to mixing instead of segregation.
Spherical shock-wave propagation in three-dimensional granular packings
Physical Review E (01/02/2011)Xue, Kun; Bai, Chun-Hua
The article investigates the spherical shock-wave propagation in an open dense granular packing. This is studied by examining the sudden expansion of a spherical intruder within the packing. The focus is on the correlation between the geometrical structure of the granular fabric and the properties of the shock-wave as it propagates through the medium. This research is crucial for understanding the mechanical behavior of granular materials under dynamic loading, which has implications in various engineering and scientific applications.
A Novel Modeling Approach for Plastics Melting within a CFD-DEM Framework
Polymers (01/01/2021)Celik, Alptekin; Bonten, Christian; Togni, Riccardo; Kloss, Christoph; Goniva, Christoph
This study introduces a novel three-dimensional modeling approach for single-screw extrusion that integrates the feed and melt sections of the process, which were traditionally considered separately. The new model, implemented within the CFDEMCoupling® framework, combines Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM) with a pioneering melting model to simulate the phase transition from solid to liquid. To validate this model, a melting apparatus was constructed and operationalized. Simulations were performed to calculate melting rates and compared with experimental outcomes, showing good alignment. This successful integration suggests the feasibility of joint CFD-DEM simulations for single-screw extruders, offering a more comprehensive analysis of the extrusion process.
Application of a hybrid Lattice Boltzmann–Finite Volume turbulence model to cyclone short-cut flow
Powder Technology (01/02/2013)Pirker, S.; Goniva, C.; Kloss, C.; Puttinger, S.; Houben, J.; Schneiderbauer, S.
This study investigates the solubility and micronization of phenacetin using supercritical carbon dioxide. The solubility was measured at pressures from 9.0 to 30.0 MPa and temperatures between 308.0 K and 328.0 K, revealing a mole fraction solubility up to 10⁻⁵. Four density-based semi-empirical models were applied to correlate the experimental data, with the Adachi-Lu-modified Chrastil model showing the best agreement. The Rapid Expansion of Supercritical Solution (RESS) process was employed to produce fine phenacetin particles, with parameters such as extraction temperature, pressure, nozzle temperature, diameter, and collection distance influencing particle size and morphology.
Regimes of liquid transport through sheared beds of inertial smooth particles
Powder Technology (01/09/2014)Mohan, Bhageshvar; Kloss, Christoph; Khinast, Johannes; Radl, Stefan
This article investigates liquid transport in moving particle beds, focusing on transfer during particle collisions and convective transport due to particle motion. Simplistic models typically handle these processes, but this study evaluates various models across different flows, ultimately selecting one for detailed shear flow simulations with soft, frictional spheres. Results from these simulations help create regime maps for effective liquid flux and draw parallels to thermal energy transport, confirming the models' accuracy. These findings aim to develop continuum models for describing liquid and thermal transport through granular materials, providing a foundation for future research.
Hybrid parallelization of the LIGGGHTS open-source DEM code
Powder Technology (01/07/2015)Berger, R.; Kloss, C.; Kohlmeyer, A.; Pirker, S.
This work presents our efforts to implement an MPI/OpenMP hybrid parallelization of the LIGGGHTS open-source software package for Discrete Element Methods (DEM). We outline the problems encountered and the solutions implemented to achieve scalable performance using both parallelization models. Three case studies, including two real-world applications with up to 1.5 million particles, were evaluated and demonstrate the practicality of this approach. In these examples, better load balancing and reduced MPI communication led to speed increases of up to 44% compared to MPI-only simulations.
Identification of DEM simulation parameters by Artificial Neural Networks and bulk experiments
Powder Technology (01/04/2016)Benvenuti, L.; Kloss, C.; Pirker, S.
This study presents a method to identify DEM simulation parameters using artificial neural networks, linking macroscopic results with microscopic parameters. An ANN is trained with varying DEM parameters to predict material behaviors, creating a database that correlates micro-level parameters with macro behaviors. This approach simplifies parameter identification for non-cohesive granular materials, requiring only one training session per experiment set to establish a generic link between experimental results and DEM parameters.
DEM study of mechanical characteristics of multi-spherical and superquadric particles at micro and macro scales
Powder Technology (01/04/2018)Soltanbeigi, Behzad; Podlozhnyuk, Alexander; Papanicolopulos, Stefanos-Aldo; Kloss, Christoph; Pirker, Stefan; Ooi, Jin Y.
This study examines the mechanical characteristics of cubical particles using Multi-spheres and Superquadrics in DEM simulations via EDEM and LIGGGHTS. Initial single particle tests assess impact, interlocking, sliding, and tilting, highlighting the importance of surface bumpiness and edge sharpness. Subsequent bulk simulations include angle of repose, Jenike shear, and silo flow tests. Results demonstrate that particle shape descriptors significantly influence bulk behavior, particularly heap profiles and shear strength in dense packings. While shape features less affect flow patterns and mass flow rates in silo discharge, they crucially impact stress distribution, underscoring the importance of accurate particle modeling in DEM studies.
Modeling of non-spherical particle flows: Movement and orientation behavior
Powder Technology (01/04/2021)Romero-Valle, Miguel Angel; Goniva, Christoph; Nirschl, Hermann
This work introduces a novel approach for calculating drag forces and torques on non-spherical particles in liquid media, addressing the technical challenges in processing particles with unconventional morphologies like fibers or flakes. Current tools fall short in predicting behaviors of these particulate systems, especially when considering particle-particle interactions and orientation, leading to costly and prolonged process development. The proposed method, integrating CFD-DEM coupling, employs Stokesian Dynamics to compute drag forces and torques, utilizing the multi-sphere method to represent non-spherical particles. This tool aims to enhance process design and understanding of non-spherical particulate systems.
A hybrid tabulation-scaling implementation of Thornton and Ning's plastic–adhesive particle contact theory
Powder Technology (01/09/2014)Loh, Jonathan C.Y.; Ketterhagen, William R.; Elliott, James A.
This paper introduces two novel implementations of the Thornton and Ning (TN) plastic-adhesive particle contact theory within the framework of the Discrete Element Method (DEM). Unlike the original TN method that uses an indirect and incremental calculation, the new approaches include a Newton-Raphson bisection (NRB) methodology for exact non-incremental contact force calculations, and a tabulation-scaling (TS) implementation that approximates the elastic-adhesive unloading curve, significantly enhancing computational speed. The TS method replicates the energy transfer of elastic-adhesive unloading within 3% of the NRB results. Using real material parameters like Young's modulus and adhesion energy, the TS approach is both physically accurate and computationally efficient. These implementations are compatible with the open-source DEM software, LIGGGHTS, facilitating broader application in simulating the behavior of plastic-adhesive particles.
Investigation of screening performance of banana screens using LIGGGHTS DEM solver
Powder Technology (01/10/2015)Jahani, M.; Farzanegan, A.; Noaparast, M.
In this numerical work, natural convection of CuO–water nanofluid and pure water in a cavity submitted to different heating modes on its vertical walls, is analyzed using the Lattice Boltzmann Method (LBM). The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. The influence of pertinent parameters such as Rayleigh number (Ra = 103–106), Hartmann number (Ha = 0–80), heat generation or absorption coefficient (q = − 10, − 5, 0, 5, 10) and nanoparticle volume concentration (ϕ = 0–0.04) on the flow and heat transfer characteristics has been examined. In general, by considering the role of Brownian motion, the enhancement in heat transfer is observed at any Hartman and Rayleigh numbers. In addition, the heat generation or absorption influences the heat transfer in the cavity at Ra = 103 more than other Rayleigh numbers as the least effect is observed at Ra = 106.
Numerical study and experimental validation of particle strand formation
Progress in Computational Fluid Dynamics, An International Journal (23/07/2009)Kahrimanovic, Damir; Kloss, Christoph; Aichinger, Georg; Pirker, Stefan
The study investigates the pneumatic conveying of spherical glass particles through a rectangular channel. A double-looping mechanism is introduced to generate a particle strand at the channel's bottom. Particle Image Velocimetry (PIV) measures particle velocity and volume concentration profiles, while numerical simulations employ the Discrete Phase Model in Fluent software. Additional sub-models address particle-wall and particle-particle collisions, as well as particle rotation effects.
Effects of nanoparticles Brownian motion in a linearly/sinusoidally heated cavity with MHD natural convection in the presence of uniform heat generation/absorption
Powder Technology (01/07/2016)Mliki, Bouchmel; Abbassi, Mohamed Ammar; Omri, Ahmed; Zeghmati, Belkacem
This study uses the Lattice Boltzmann Method (LBM) to analyze natural convection of CuO-water nanofluid and pure water within a differently heated cavity. It employs the KKL correlation for determining the nanofluid's effective thermal conductivity and viscosity. The effects of various parameters such as Rayleigh number (Ra = 10^3 to 10^6), Hartmann number (Ha = 0 to 80), heat generation/absorption coefficient (q = -10 to 10), and nanoparticle volume concentration (ϕ = 0 to 0.04) on flow and heat transfer are explored. Results show enhanced heat transfer due to Brownian motion across all tested Hartmann and Rayleigh numbers, with heat generation or absorption impacting heat transfer most significantly at the lowest Rayleigh number (Ra = 10^3).
Regimes of subsonic compressible flow in gas-particle systems
Powder Technology (01/12/2021)Mačak, Jelena; Goniva, Christoph; Radl, Stefan
This study introduces regime maps for subsonic flow in dense gas-particle systems, distinguishing between compressible and effectively incompressible flow areas. These maps are valuable for guiding researchers and industry professionals in selecting modeling techniques and verifying numerical solvers. The findings challenge the traditional compressibility threshold of Mach 0.3, showing significant compressible effects in porous media flows even at lower Mach numbers (
Coupled CFD–DEM simulation of fluid–particle interaction in geomechanics
Powder Technology (01/05/2013)Zhao, Jidong; Shan, Tong
Jet-milling is a particle engineering process widely adopted in industrial manufacturing to reduce the particle size of powders. Computational Fluid Dynamics simulations (CFD) coupled with Discrete Element Modelling (DEM) proved to be a valuable tool to tackle the complexity and the non-linearity of particle breakage and classification occurring in mills. To date however, they have been employed to address only single aspects of process design being unable to reproduce it completely. The coupled CFD-DEM simulations presented in this work are for the first time capable of simultaneously describe particle fragmentation, particle-gas interaction and classification. Through coarse-graining, realistic amounts of powder can be simulated allowing to demonstrate/study how the hold-up mass slows down the milling gas affecting classification and thus the milling performance. Bottlenecks/limitations of model and methodology are critically examined to understand what is currently preventing us from creating a digital twin of the milling process.
4-way coupling CFD-DEM simulation of particle breakage and classification in a spiral jet mill: A critical analysis
Powder Technology (01/04/2024)Bnà, S.; Bottau, F.; Niemann, M.; Goniva, C.; Cottini, C.; Benassi, A.
This paper explores the advancement of Computational Fluid Dynamics (CFD) coupled with Discrete Element Modeling (DEM) in simulating jet-milling processes, crucial for reducing particle sizes in industrial manufacturing. Traditionally, CFD-DEM has addressed only specific aspects of milling due to its complexity. For the first time, this study integrates particle fragmentation, particle-gas interaction, and classification in a single simulation, enhancing process design comprehensiveness. Through coarse-graining techniques, the simulation manages realistic powder volumes, revealing how mass hold-up decelerates milling gas, impacting classification and overall milling efficiency. The study also identifies current limitations in modeling, crucial for progressing towards a fully-functional digital twin of the milling process.
A modified cohesion model for CFD–DEM simulations of fluidization
Powder Technology (01/08/2016)Gu, Yile; Ozel, Ali; Sundaresan, Sankaran
CFD-DEM simulations analyzed gas-fluidization in particles with van der Waals cohesion for Group A and Group C particles. The study revealed that using lower spring constants in simulations, compared to real-world values, affects flow patterns. A modified cohesion model, validated through two-particle collision analysis, showed that for Group A particles, bubble size distribution remained consistent regardless of stiffness, while Group C particles maintained stable flow patterns unless stiffness was extremely low. The model effectively handled mildly cohesive Group A particles but was less accurate for strongly cohesive Group C particles, where large agglomerates formed, confirming earlier findings by Kobayashi et al. (2013).
Coarse Graining for Large-scale DEM Simulations of Particle Flow – An Investigation on Contact and Cohesion Models
Procedia Engineering (09/04/2015)Nasato, Daniel Schiochet; Goniva, Christoph; Pirker, Stefan; Kloss, Christoph
This paper builds on previous research to evaluate the scalability of the linear spring dashpot (LSD) contact law through shear test box simulations with Lees-Edwards boundary conditions. The study expands to compare the LSD model with the Hertz contact model and briefly explores the Johnson-Kendall-Roberts (JKR) cohesive contact model. Results indicate that the Hertz model behaves similarly to the scaled LSD model in both inertial and quasi-static regimes. For coarse-graining scenarios, both models maintain nearly constant stress levels in the quasi-static regime, whereas stress significantly increases in the inertial regime. The paper also provides preliminary findings on the JKR model.
Parallel open source CFD-DEM for resolved particle-fluid interaction
Proceedings of 9th International Conference on Computational Fluid Dynamics in Minerals and Process Industries (10/12/2012)Hager, Alice; Kloss, Christoph; Pirker, Stefan; Goniva, Christoph
This paper presents a parallelized resolved method for simulating immersed body dynamics in fluids using the Fictitious Domain Method (FDM). The approach couples the Lagrangian Discrete Element Method (DEM) for body tracking with Computational Fluid Dynamics (CFD) for fluid flow and pressure calculation. The algorithm alternates between CFD calculations, body velocity inclusion, and force corrections to ensure conservation equations are met. Dynamic local mesh refinement minimizes fluid cells near bodies. Integrated into the CFDEMcoupling framework, combining LIGGGHTS and OpenFOAM®, the parallelization enables large-scale simulations. Validation includes flow around settling and rotating spheres, and studies of the Boycott effect.
Towards fast parallel CFD-DEM: An open-source perspective
Proceedings of open source CFD international conference (01/01/2009)Goniva, Christoph; Kloss, Christoph; Pirker, Stefan
This paper introduces "LammpsFoam," a coupled CFD-DEM solver combining LAMMPS for discrete element modeling and OpenFOAM® for fluid dynamics. Building on previous work coupling EDEM and FLUENT, this new solver overcomes the limitations of shared memory systems by enabling parallel simulations on distributed memory machines using MPI. The approach accounts for volume displacement, particle drag, and Magnus force, making it suitable for a wide range of particle-fluid systems. The paper outlines the modeling strategy, validates the solver with a test case, and provides an outlook for future applications in handling computationally intensive industrial problems.
An open source CFD-DEM perspective
Proceedings of OpenFOAM Workshop, Göteborg (02/07/1905)Goniva, Christoph; Kloss, Christoph; Hager, Alice; Pirker, Stefan
This paper introduces a coupled solver combining the Discrete Element Method (DEM) for granular material behavior, using LIGGGHTS, and Computational Fluid Dynamics (CFD) for interstitial fluid flow, using OpenFOAM®. Designed for large-scale industrial problems, the solver supports fully parallel simulations on distributed memory machines via MPI. This integration enables efficient handling of computationally intensive problems. Validation through test cases demonstrates accurate predictions of pressure drop and minimum fluidization velocity, showcasing the solver's capability for realistic industrial applications.
The birth of a dinosaur footprint: Subsurface 3D motion reconstruction and discrete element simulation reveal track ontogeny
Proceedings of the National Academy of Sciences (01/12/2014)Falkingham, Peter L.; Gatesy, Stephen M.
This study reconstructs 3D foot movements of guineafowl walking on granular substrates using biplanar X-rays and integrates the data into discrete element method (DEM) simulations. The combination reveals how foot motion causes sediment deformation both at the surface and subsurface "virtual bedding planes," exposing organized subsurface tracks despite surface collapse. The longest toe penetrates ~5 cm at a 30° angle before slipping backward on withdrawal. These insights uncover how track features form through localized deformations, termed "track ontogeny," offering a mechanistic link between limb motion, substrate dynamics, and track morphology, enhancing fossil track interpretation and understanding of deformable substrate locomotion.
Comprehensive DEM-DPM-CFD simulations-model synthesis, experimental validation and scalability
Proceedings of the seventh international conference on CFD in the minerals and process industries, CSIRO, Melbourne, Australia (09/12/2009)Kloss, Christoph; Goniva, Christoph; Aichinger, Georg; Pirker, Stefan
This study combines the Discrete Element Method (DEM) for granular material behavior with a finite volume Computational Fluid Dynamics (CFD) model for interstitial fluid flow. To reduce computational costs, DEM is complemented by the Discrete Phase Model (DPM) for dispersed granular flow using spatial domain decomposition, enabling both models to operate within a single simulation. The implementation supports fully parallel simulations for all three models. The approach's efficiency and accuracy are validated through three examples, and its scalability is discussed, highlighting its suitability for large-scale coupled fluid-granular flow simulations.
Describing the Drying and Solidification Behavior of Single Suspension Droplets Using a Novel Unresolved CFD-DEM Simulation Approach
Processes (01/02/2024)Buchholz, Moritz; Weis, Dominik; Togni, Riccardo; Goniva, Christoph; Heinrich, S.
This study introduces an unresolved CFD-DEM simulation approach to model the drying and solidification of single suspension droplets in a spray dryer. Solidification begins when a critical solid concentration is reached at the droplet surface, forming bonds between primary particles. Drying conditions are derived from large-scale spray dryer simulations for different droplet sizes. Results show that higher drying rates promote hollow particle formation when solidification occurs early. The findings help identify optimal spray dryer operating conditions to achieve desired particle morphologies, advancing simulation-based process and product design for spray-dried products.
Towards efficient simulation of off-gas scrubbing by a hybrid Eulerian Lagrangian model
Progress in Computational Fluid Dynamics, An International Journal (27/09/2010)Goniva, Christoph; Tukovic, Zeljko; Feilmayr, Christoph; Pirker, Stefan
This research presents a hybrid Eulerian–Lagrangian model for simulating wet scrubbers used in capturing fine dust particles from off-gas streams. The model traces representative droplets in a Lagrangian manner while treating dust as passive Eulerian phases. It also incorporates a wall film model that solves shallow water equations, accounting for droplet deposition, film separation, and stripping. Numerical results for pressure drop and capturing efficiency align well with experimental measurements, indicating the model's effectiveness in simulating the scrubbing process.
Models, algorithms and validation for opensource DEM and CFD-DEM
Progress in Computational Fluid Dynamics, An International Journal (26/06/2012)Kloss, Christoph; Goniva, Christoph; Hager, Alice; Amberger, Stefan; Pirker, Stefan
This study presents a versatile framework for simulating coupled fluid-granular systems using the Discrete Element Method (DEM) for particle motion and Computational Fluid Dynamics (CFD) for interstitial fluid flow. It details two coupling approaches: unresolved CFD-DEM and resolved CFD-DEM with an Immersed Boundary (IB) method. Both methods are validated against analytical solutions and experimental data, demonstrating their effectiveness in modeling complex fluid-particle interactions.
Multi-scale Analysis of Turbulent Rayleigh-Bénard Convection
Progress in Turbulence VI (03/03/2016)Togni, Riccardo; Cimarelli, Andrea; De Angelis, Elisabetta
This study presents results from a direct numerical simulation of turbulent Rayleigh-Bénard convection at a Rayleigh number of RaRa and Prandtl number of 0.7. The flow is dominated by coherent thermal plumes, localized regions of fluid with a temperature contrast. Using the wall-parallel divergence of the velocity field, two key near-wall events are identified: plume impingement and ejection. Impingement leads to the formation of larger structures in velocity and temperature fields, suggesting a reverse energy transfer from small to large scales in the near-wall region, challenging the classical turbulence picture of energy cascading from large to small scales.
Towards an Improved Subgrid-Scale Model for Thermally Driven Flows
Progress in Turbulence VII (27/06/2017)Togni, Riccardo; Cimarelli, Andrea; De Angelis, Elisabetta
This study investigates the effect of spectral cutoff filtering on the resolved and subgrid dynamics of turbulent Rayleigh–Bénard convection (RBC) using Direct Numerical Simulation (DNS) data. For small filter lengths, resolved processes closely match exact dynamics, with reduced dissipation balanced by subgrid-scale sinks. At larger filter lengths, resolved dynamics near walls deplete, and subgrid-scale behavior becomes more complex, deviating from purely dissipative effects. The findings suggest that conventional eddy-viscosity and diffusivity models used in large-eddy simulations may fail for large filters, highlighting the need for alternative closure models to accurately capture subgrid-scale effects in RBC systems.
Simulation Partikelbeladener Strömungen: Diskrete, Kontinuierliche Und Hybride Modellierungsansätze
Pulvermetallurgie in Wissenschaft und Praxis. (01/11/2014)Pirker S.; Schiochet Nasato D.; Benvenuti L.; Kloss C.; Schneiderbauer S.
Prozesse der Pulvermetallurgie basieren auf einer großen Anzahl kleiner (meist polydisperser), fester Partikel. In einigen Prozessschritten (Pulvervorbehandlung, Formfüllen) lässt sich das makroskopische Pulververhalten durch einen Strömungszustand beschreiben, der durch eine zusätzlich vorhandene Gasphase beeinflusst werden kann. Basierend auf einem illustrativen Beispiel einer Pulverentmischung in einer bi-dispersen Wirbelschicht werden kontinuierliche und diskrete state-of-the-art-Simulationsmodelle präsentiert und deren individuelle Stärken und Limitationen diskutiert. Schließlich wird ein Ausblick auf neue, hybride Modellierungskonzepte gegeben, um komplexe Pulverströmungen abbilden zu können. Der Vortrag schließt mit der Vorstellung einer gemeinschaftlichen, internationalen Plattform für die Entwicklung von Simulationswerkzeugen für partikelbeladene Strömungen.
Sediment erosion a numerical and experimental study
River Flow 2012 - Proceedings of the International Conference on Fluvial Hydraulics (01/01/2012)Goniva, Christoph; Gruber, K.; Kloss, Christoph
A new numerical model to describe the erosion process in the presence of a free surface flow is proposed and tested against experimental data. The fluid flow is captured by a Computational Fluid Dynamics (CFD) method, whereas the sediment is modelled at a grain size level using Discrete Element Method (DEM). The fluid-particle interaction is realized by a coupling of CFD and DEM, capturing the physics of sediment erosion and deposition at a very detailed particle-scale level.With the aid of optical and acoustic measurement techniques (PIV,ADV) the fluid flow as well as turbulence downstream of a weir is investigated experimentally. Using a LASER based measuring device local bed erosion downstream of the hydraulic structure is analysed and compared to numerical results. It is shown that for numerical simulations different turbulence models are able to capture the global flow pattern but have significant influence on predicted erosion rates. The numerical model presented in this paper is completely realized in an open source environment.
State of the art in mapping schemes for dilute and dense Euler-Lagrange simulations
Selected papers from 10th International Conference on Computational Fluid Dynamics in the Oil & Gas, Metallurgical and Process Industries (07/07/1905)Radl, Stefan; Gonzales, Begona C.; Goniva, Christoph; Pirker, Stefan
This study presents enhanced Euler-Lagrange (EL) simulations for gas-particle flows using robust Lagrangian-to-Euler mapping schemes. By integrating field smoothing techniques from Pirker et al. (2011) and Capecelatro and Desjardins (2013), the new schemes support implicit, explicit, and hybrid time marching, enabling simulations of highly loaded flows with broad particle size distributions. Performance is demonstrated across three cases: (i) a bubbling bi-disperse fluidized bed, (ii) freely sedimenting suspension, and (iii) particle injection in a turbulent cross-flow. The results highlight the schemes' accuracy and versatility for complex gas-particle flow systems in academic and industrial applications.
Thermofluidic compression effects to achieve combustion in a low-compression scramjet engine
Shock Waves (01/07/2018)Moura, A. F.; Wheatley, V.; Jahn, I.
This study investigates thermofluidic compression effects in scramjet inlets using Reynolds-averaged Navier–Stokes simulations. A simplified scramjet engine with insufficient inlet compression was tested, featuring a wide rectangular combustor and a central hydrogen injector. Higher fuel equivalence ratios (0.22, 0.17, 0.13) led to earlier ignition and faster combustion, driven by local compression from the increased mass flow rate. Supplementary helium injections confirmed this effect. The higher mass flow generated stronger injector bow shocks, compressing the free-stream gas, increasing OH radical production, and promoting ignition. Subsequent heat release provided thermal compression, boosting downstream pressure, temperature, and overall combustion efficiency.
Correction to: Thermofluidic compression effects to achieve combustion in a low-compression scramjet engine
Shock Waves (01/06/2019)Moura, A. F.; Wheatley, V.; Jahn, I.
This study examines the role of thermofluidic compression in scramjet inlets, using Reynolds-averaged Navier–Stokes simulations. A simplified scramjet engine with low inlet compression was analyzed, featuring a wide rectangular combustor and central hydrogen injector. Increasing the fuel injection mass flow rate (equivalence ratios of 0.22, 0.17, and 0.13) led to earlier ignition and faster combustion due to local compression. Stronger injector bow shocks compressed the free-stream gas, enhancing OH radical production and ignition. Heat release from combustion further provided thermal compression, boosting downstream pressure, temperature, and combustion efficiency, demonstrating that fuel injection can compensate for insufficient inlet compression.
Parallel Resolved Open Source CFD-DEM: Method, Validation and Application
The Journal of Computational Multiphase Flows (01/03/2014)Hager, A.; Kloss, C.; Pirker, S.; Goniva, C.
In the following paper the authors present a fully parallelized Open Source method for calculating the interaction of immersed bodies and surrounding fluid. A combination of computational fluid dynamics (CFD) and a discrete element method (DEM) accounts for the physics of both the fluid and the particles. The objects considered are relatively big compared to the cells of the fluid mesh, i.e. they cover several cells each. Thus this fictitious domain method (FDM) is called resolved. The implementation is realized within the Open Source framework CFDEMcOupling ( www.cfdem.com ), which provides an interface between OpenFOAM® based CFD-solvers and the DEM software LIGGGHTS ( www.liggghts.com ). While both LIGGGHTS and OpenFOAM® were already parallelized, only a recent improvement of the algorithm permits the fully parallel computation of resolved problems. Alongside with a detailed description of the method, its implementation and recent improvements, a number of application and validation examples is presented in the scope of this paper.
Coupled LBM–DEM Micro-scale Simulations of Cohesive Particle Erosion Due to Shear Flows
Transport in Porous Media (01/08/2015)Brumby, Paul E.; Sato, Toru; Nagao, Jiro; Tenma, Norio; Narita, Hideo
This paper investigates the erodibility of cohesive micro-scale particles under varying surface shear stresses using a coupled lattice Boltzmann method (LBM) and discrete element method (DEM). Compacted layers of 100 cohesive spheres are subjected to shear flow, revealing a critical shear stress threshold for erosion. Beyond this threshold, the erosion rate increases linearly with excess surface shear stress. Additionally, an upward motion mechanism for detached particles is observed. The study highlights the potential of the LBM-DEM approach for modeling dynamic erosion processes in three dimensions, offering insights into fluid-particle interactions in cohesive particle systems.
Laboratory Tests and Numerical Simulations of Mixing Superheated Virgin Aggregate with Reclaimed Asphalt Pavement Materials
Transportation Research Record (01/01/2015)Zhang, Kun; Wen, Haifang; Hobbs, Andrew
This study examines the heating and binder transfer of reclaimed asphalt pavement (RAP) during mixing with superheated virgin aggregate, focusing on factors affecting blending efficiency. Laboratory tests and Discrete Element Method (DEM) simulations were conducted to analyze temperature evolution and RAP binder transfer in a drum mixer. Results showed that longer mixing times or higher virgin aggregate temperatures are required for high RAP content or high RAP moisture. DEM simulations proved effective for studying the mixing process and can be used in the future to optimize production processes for RAP mixes, improving sustainability without compromising pavement performance.
Combined experimental and numerical approach for wear prediction in feed pipes
Tribology International (01/09/2013)Varga, Markus; Goniva, Christoph; Adam, Karl; Badisch, Ewald
This study combines experimental and numerical approaches to investigate erosive wear in feed pipes. Lab-scale tests revealed that erosion rates depend on material properties and impact angles: steel experiences more wear at higher impact angles, while rubber is more affected at lower angles. Empirical erosion models fail to capture material-dependent critical impact energies and fatigue effects. A CFD-DEM approach was used to simulate particulate flow in pipes, and long-term wear measurements tracked wear progression. While further validation is required, the results show promising potential for accurate erosion prediction, enhancing understanding of wear processes in industrial applications.
Plastic Accumulation in Front of a Plate in Cross Flow: Model Scale Test and CFD-DEM Modelling
ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering (01/06/2019)Wrenger, Hendrik; Sainte-Rose, Bruno; Goniva, Christoph; Hilbert, Renan
This study presents results from flume experiments and CFD-DEM simulations of plastic accumulation in front of a fixed plate, simulating ocean cleanup systems. Experiments examined flow velocity, plate draft (Froude number), and three plastic particle types, observing accumulation profiles under increasing loads. A linear relationship between relative accumulation depth and plate Froude number was identified for specific particle types. The open-source CFDEM® code, coupling LIGGGHTS® and OpenFOAM®, successfully reproduced the experimental results. Limitations of the experimental setup and single-phase CFD-DEM approach were discussed, highlighting the need for further calibration and research to improve accuracy and applicability.
Supplemental Proceedings: Materials Fabrication, Properties, Characterization, and Modeling
TMS 2011 Annual Meeting (01/02/2011)The Minerals, Metals & Materials Society (TMS)
The "TMS 2011 Annual Meeting Supplemental Proceedings, Volume 2: Materials Fabrication, Properties, Characterization, and Modeling" compiles research presented at the 2011 TMS Annual Meeting and Exhibition. This volume encompasses studies on materials fabrication techniques, property analysis, characterization methods, and modeling approaches, offering insights into advancements in materials science and engineering.
Discrete Element Method Modeling of Laser Beam Absorption on Rough Surfaces and Powder Beds
Materials Engineering (01/10/2023)Lupo, Giandomenico; Niemann, Martin; Goniva, Christoph; Szmyt, Wojciech; Jia, Xiao; Turlo, Vladyslav
The energy transfer from a laser beam source to material surfaces with arbitrary geometrical features and variable surface roughness is the crucial step in many high-end engineering applications. We present a high-fidelity numerical framework for the simulation of laser beam interaction with such surfaces, which include meshed geometry of arbitrary shape and material Lagrangian particles. The method discretizes the laser source as a collection of photon-type immaterial Lagrangian particles and is able to capture the effects of multiple reflections, angle-dependent reflectivity, and polarization change. Validation is conducted against the experimental measurement of the effective reflectivity of a rough copper sample, revealing the impact of the polarization effects. The method is also applied to powder beds and powder layers, and a new theoretical algebraic model for the effective reflectivity of powder layers versus layer sparseness is proposed, based on the simulation data.
DEM-PM Contact Model with Multi-Step Tangential Contact Displacement History
Simulation-Based Engineering Laboratory (07/07/1905)Fleischmann, J.
This study provides an overview of the Discrete Element Method (DEM) for granular flow and geomechanics, focusing on the Penalty Method (PM) for soft-body contacts. A new multi-time-step tangential contact displacement history model is introduced and validated through direct shear tests using the Chrono DEM solver. Comparisons with models lacking tangential history show significant under-prediction of shear stress by a factor of ten. Results from Chrono agree well with experiments on glass spheres and simulations from LIGGGHTS. The study confirms the model's accuracy in replicating physical geomechanical tests, highlighting its effectiveness in capturing realistic shear behavior in granular materials.
Simulation of fluid suspended particle behaviour subject to transverse standing acoustic fields
Progress in Computational Fluid Dynamics, An International Journal (04/07/1905)Dabic, Mihajlo
This computational study examines the effectiveness of standing wave acoustic fields for deflecting quartz particles in water through a vertically oriented parallelepiped duct (50×50×70 cm³). Using OpenFOAM (CFD), LIGGGHTS (DEM), and CFDEM coupling, the model simulates drag, buoyancy, gravity, and acoustic forces in idealized conditions. Particles (5–30 μm) were carried at flow speeds of 0.1, 0.5, and 1 m/s while subject to acoustic forces at two frequencies (14,794 Hz and 26,629 Hz). Results show frequency influences deflection efficiency, nodal distribution, and particle residence time. The model demonstrates qualitative agreement with theoretical trends, validating its applicability for particle deflection studies.
CFD-DEM on Multiple Scales - An Extensive Investigation of Particle-Fluid Interactions
Johannes Keppler Univeryity, Linz (01/06/2014)König, Alice
This thesis focuses on simulating particle-laden flows using coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). Resolved CFD-DEM, applied for detailed analysis of a few large particles, involved developing a parallelized Fictitious Domain Method (FDM), validated through examples like Boycott’s blood cell settling case. For large particle systems, unresolved CFD-DEM analyzed blast air-induced cavities (raceways) in blast furnaces. A pseudo-2D lab model provided experimental validation, revealing 2D effects. This led to 3D simulations of a full-scale blast furnace. The tools and solvers developed were integrated into the Open Source CFDEMproject, advancing methods for both resolved and unresolved particle-laden flows.
Modeling proppant flow in fractures using LIGGGHTS, a scalable granular simulator
The University of Texas Austin (01/05/2014)Shor, Roman J.
This study uses a Discrete Element Method (DEM) model to simulate proppant flowback in fractures under confining pressures, analyzing fracture width, confining stress, flow velocity, and proppant cohesion. Results reveal three regimes: full fracture evacuation at high flow rates and low stress, fully packed fractures at high stress, and partially evacuated fractures in intermediate conditions. Proppant production depends on cohesion, while fracture width is influenced by stress and flow velocity. A controlled, gradual well flowback rate, adjusted for leak-off coefficient, is recommended to stabilize the proppant pack and reduce costly flow restrictions and equipment damage.
A computational framework for coupled modelling of three-phase systems with soluble surfactants
# (04/07/1905)Wierink, Gijsbert Alexander
This study presents a comprehensive CFD-DEM modeling framework for bubble-particle interaction in the presence of soluble surfactants, relevant for industrial processes like froth flotation. The framework couples OpenFOAM (CFD) and LIGGGHTS (DEM) via CFDEM, incorporating gas-liquid-solid momentum coupling and the Volume of Fluid (VOF) method for bubble surface dynamics. Particle-interface forces are modeled as hyperbolic functions of phase fraction gradients, including DLVO, non-DLVO, and inertial forces. Soluble surfactant effects are represented through a volumetric transport equation for interfacial tension. The model is modular, mass-conservative, and extensible for future developments, offering a significant advancement in flotation system simulations.
Modeling of Laser Beam Absorption on Rough Surfaces, Powder Beds and Sparse Powder Layers
Results in Physics (01/06/2024)Lupo, Giandomenico; Niemann, Martin; Goniva, Christoph; Szmyt, Wojciech; Jia, Xiao; Turlo, Vladyslav
This study introduces two models to predict energy transfer from a laser beam to surfaces with arbitrary geometry and variable roughness. The first is a high-fidelity numerical framework using the Discrete Element Method (DEM) to simulate photon-particle interactions, accounting for multiple reflections, angle-dependent reflectivity, and polarization changes. Validation against rough copper surfaces highlights the significance of polarization effects. The second model is a phenomenological correlation for predicting effective reflectivity of sparse powder layers, such as recondensed metal vapor in laser welding. The correlation aligns well with simulation results and experimental data, offering tools for diverse laser-material interaction scenarios.
Approximation of objects by spheres for multisphere simulations in DEM
This paper presents a novel grid-based method to approximate non-convex, closed objects using a finite number of spheres, addressing limitations in simulating granular systems with spherical particles. Implemented in LIGGGHTS, the method enables multi-sphere approximations of objects defined by stereo-lithography files, such as laser-scanned surface data. The process involves grid creation, sphere placement based on grid-point data, volume calculation, and scaling to match the object’s volume. A quality measure is introduced to evaluate approximations. Results demonstrate the method's effectiveness, providing a practical tool for simulating non-spherical particles in discrete element simulations.
Combining Open Source and Easy Access in the field of DEM and coupled CFD-DEM: LIGGGHTS®, CFDEM®coupling and CFDEM®workbench
Discrete Element Method (DEM) and its combination with Computational Fluid Dynamics (CFD-DEM) are essential for designing and optimizing particle processes in various industries such as pharmaceuticals, agriculture, and manufacturing. The open source software, CFDEM®coupling and LIGGGHTS®, offer advanced simulation capabilities. However, the complexity of installing and using these tools can be a barrier for many potential users. To address this, the commercial GUI CFDEM®workbench was developed to simplify the use of these powerful simulation tools while maintaining the benefits of open source software. It assists users in installation and setup, facilitating access to sophisticated DEM and CFD-DEM modeling in sectors ranging from steel to plastics production.
Direct Numerical Simulation of a Buoyant Droplet Array
This research focuses on Direct Numerical Simulation (DNS) of approximately 1,000 inertial droplets in a turbulent carrier fluid, incorporating physical models for coalescence and breakup. The study addresses the computational challenges of such simulations, demonstrating that their code scales efficiently with increasing numbers of deformable droplets and larger grid sizes. This advancement enhances the understanding of droplet dynamics and turbulence interactions, particularly in clustering regimes where the Stokes number is around 1.
Tree root mounds and their role in transporting soil on forested landscapes
The study explores how tree roots contribute to soil movement on hillslopes by examining soil mounding around Ponderosa and Lodgepole pine trees in Colorado's Boulder Creek watershed. Soil mounds around these trees show significant vertical displacements up to 20 cm, indicating that tree roots actively displace and mix the surrounding soil. This displacement is not merely due to soil flow around the tree but is caused by root volume expansion in all directions. The study uses a discrete element model (LIGGGHTS) to simulate root growth and the resulting soil mounding, confirming that root growth can substantially alter soil density and topography. This research underscores the importance of root dynamics in soil transport processes on forested slopes.
Decoding the structure of granular and porous materials from speckled phase contrast X-ray images
The paper discusses a new thermal lens effect utilizing a laser beam with Orbital Angular Momentum (OAM). The study investigates how the OAM properties of a laser can influence the formation of thermal lenses, a phenomenon where the medium's refractive index changes due to temperature gradients caused by laser heating. This research is significant for advancing our understanding of light-matter interactions in optically active and thermal-sensitive environments, providing insights into the dynamic processes involved and potential applications in optical systems.
Correct Boundary Conditions for Turbulent SPH
This publication discusses the formulation of correct boundary conditions for turbulent flows using the Smoothed Particle Hydrodynamics (SPH) method. It introduces unified and consistent boundary conditions for 2D SPH for weakly compressible flows, covering wall impermeability, wall shear stress, and wall turbulent conditions using the k-ε model. Additionally, it addresses inlet-outlet open boundaries, aiming to enhance the accuracy and applicability of SPH simulations in engineering and physics. This approach is crucial for modeling complex fluid dynamics in various practical and industrial applications.
Eddy interaction model for turbulent suspension in Reynolds-averaged Euler–Lagrange simulations of steady sheet flow
The article from Elsevier discusses the effectiveness of different treatment regimens for latent tuberculosis infection (LTBI). It aims to provide evidence-based insights to assist policymakers in designing national treatment policies and protocols. The study uses the PRISMA-NMA method to review and synthesize existing data on the efficacy, adherence, and safety of various LTBI treatments, emphasizing the need for tailored approaches to prevent the progression to active tuberculosis.
Characterization of Supersonic Turbulent Combustion in a Mach-10 Scramjet Combustor
This paper discusses modal decomposition techniques as a tool for simplifying the complex dynamics of fluid flows by breaking them down into fundamental components or modes. These techniques, which include methods like Proper Orthogonal Decomposition and Dynamic Mode Decomposition, are valuable for capturing key dynamic features of fluid systems across various conditions, facilitating more efficient analysis and modeling. This approach is particularly useful in engineering and physics to develop low-dimensional models of complex systems, enhancing both computational and experimental methodologies.
Correction: Characterization of Supersonic Turbulent Combustion in a Mach-10 Scramjet Combustor
The paper discusses modal decomposition techniques, which simplify the dynamics of fluid flows by breaking them down into fundamental components or modes. These techniques are instrumental for capturing essential dynamic features across various conditions, thereby aiding in the development of low-dimensional models for complex systems. This approach optimizes both computational and experimental methodologies in engineering and physics.
Effects of Oxygen Enrichment on Supersonic Combustion in a Mach 10 Scramjet
The paper explores the effects of oxygen enrichment on supersonic combustion in scramjet engines operating at Mach 10. It discusses the benefits of premixing fuel with oxygen to enhance combustion efficiency at high altitudes where oxygen levels are otherwise insufficient. This technique aims to expand the operational envelope of scramjets, traditionally limited by atmospheric oxygen availability, thereby offering a more versatile solution for high-speed aerial and space propulsion systems.
A redefined energy functional to prevent mass loss in phase-field methods
The article explores an updated energy functional designed to prevent mass loss in phase-field models. The new functional includes terms that account for both bulk energy density and excess energy due to inhomogeneous distribution in the interfacial regions. This redefined energy functional helps in ensuring a proper energy balance while preventing nonphysical bulk diffusion, thus improving the conservation of mass in computational simulations that use phase-field methods.
Improving the applicability of discrete phase simulations by smoothening their exchange fields
This study addresses the limitations of the Discrete Phase Model (DPM) in simulating particle-laden flows, particularly its inability to account for particle collisions and the resulting overestimation of particle dispersion. The authors propose an enhanced DPM approach that incorporates a stochastic collision model to simulate particle-particle interactions. Validation against experimental data demonstrates improved accuracy in predicting particle dispersion and concentration profiles, making this method more reliable for engineering applications involving particulate flows.
Floating electrode optoelectronic tweezers: Light-driven dielectrophoretic droplet manipulation in electrically insulating oil medium
The research introduces Floating Electrode Optoelectronic Tweezers (FEOET), a mechanism for manipulating aqueous droplets in electrically insulating oil using light-induced dielectrophoresis. FEOET employs a photoconductive glass layer to create virtual electrodes with direct optical images, enabling light-driven transport of droplets. This technique offers a versatile and efficient method for droplet manipulation in microfluidic applications.
Molecular Dynamics simulation for PBR pebble tracking simulation via a random walk approach using Monte Carlo simulation
This paper introduces a new energy functional within phase-field models to address mass conservation issues. The redefined functional helps avoid nonphysical bulk diffusion and ensures a proper energy balance, thereby improving the model's accuracy in simulating phenomena where mass loss is critical, such as in materials science and phase transitions.
Efficient Scalable Simulation of Burden Flow Using a Non-spherical Particle: DEM Approach
This study presents a numerical model for simulating burden flow in blast furnaces, integrating Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM). The model emphasizes non-spherical particle shapes to closely replicate physical phenomena. This approach enhances the accuracy of simulations, providing valuable insights into the complex behaviors of granular materials in industrial processes.
A resolved two-way coupled CFD/6-DOF approach for predicting embolus transport and the embolus-trapping efficiency of IVC filters
The paper introduces a resolved two-way coupled Computational Fluid Dynamics (CFD) and Six Degrees of Freedom (6-DOF) approach for simulating the movement of emboli in the cardiovascular system and evaluating the trapping efficiency of Inferior Vena Cava (IVC) filters. IVC filters are designed to prevent the passage of emboli from the lower extremities to the heart and lungs, which can cause severe complications such as pulmonary embolism. This model aims to enhance the understanding and effectiveness of IVC filters by providing a detailed simulation that includes both fluid dynamics and the filter's physical response to emboli.
Transfer chutes: Predicting dust emissions by multiphase CFD and coupled DEM-CFD simulations
Dust emission is one of the main problems in the operation of transfer chutes. The design of the transfer chute heavily influences any potential dust generation. Although this influence is well known, much more attention is given to active dust suppression via water spray systems, the exhaustion of the dust polluted air or the use of electrostatic filters rather than the design optimization of the transfer chute.
Simulation of wear and dust emission at a transfer chute
In this contribution the dust emission and wear at a transfer chute is investigated by means of numerical simulations using a coupled Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). This flexible and detailed modelling approach helps to obtain an insight into dust generation and propagation as well as wear in industrial plants. The first part of this paper deals with the optimization of a transfer chute in terms of dust emission and the second part deals with local wear prediction.
A comprehensive frictional-kinetic model for gas–particle flows: Analysis of fluidized and moving bed regimes
This study introduces a comprehensive frictional-kinetic model for gas–particle flows, treating both gas and particles as continua. The model integrates the kinetic theory of granular flows to account for kinetic-collisional stresses and employs inertial number-dependent rheology alongside dilation laws to represent frictional stresses. This approach effectively captures the transition between collisional and frictional regimes in dense granular flows, enhancing the accuracy of simulations in various engineering applications.
Experimental and numerical investigation of sloshing resonance phenomena in a spring-mounted rectangular tank
Inspired by the dynamics observed in a steelmaking converter, this study examines liquid sloshing using a simplified experimental setup with a rectangular tank mounted on a spring-controlled seesaw. The experiments addressed various scenarios: a collapsing water column and gas injection-induced sloshing in both fixed and spring-mounted tanks. In spring-mounted configurations, the study highlighted that when the mechanical eigenfrequency of the suspension system aligns with the wave frequencies, a resonance occurs, leading to beat-like energy transfers that periodically increase and decrease the load on the system. These findings are supported by analytical evaluations and 3D multiphase flow simulations, which generally align with the experimental results but show artificially damped sloshing motions.
Fluid and particle coarsening of drag force for discrete-parcel approach
Fine-grid Euler–Lagrange simulations were performed to study gas-fluidization of uniformly sized particles in three-dimensional periodic domains. These simulations were coarse-grained to derive filter size dependent corrections for drag laws in Euler–Euler (EE) and Multi-Phase Particle-in-Cell (MP-PIC) models. The corrections mostly stem from fluid cell coarsening rather than particle phase coarsening. This discovery indicates that drag models developed for coarse EE simulations are also applicable to MP-PIC simulations, facilitating mutual drag correction applicability between these simulation types.
Handling contact points in reactive CFD simulations of heterogeneous catalytic fixed bed reactors
This study focuses on the crucial role of mesh generation in Computational Fluid Dynamics (CFD) simulations, particularly for handling contact points in random packed beds of spheres. It systematically investigates the treatment of contact points in reactive gas-solid packed bed simulations, building on prior research on radial heat transfer and pressure drop. The study extends and evaluates the bridge method to surface reactions, beginning with an analysis of a regular bed of spheres under laminar conditions (Re~80). This setup allows for precise meshing at contact points, enabling explicit comparisons between meshes with and without bridges. From these comparisons, guidelines are developed and tested on the meshing of a random packed bed reactor, establishing a meshing protocol that ensures accurate descriptions of surface reactivity, pressure drops, and heat transfer in packed bed reactors.
Color-PTV measurement and CFD-DEM simulation of the dynamics of poly-disperse particle systems in a pseudo-2D fluidized bed
In this study, a novel color particle tracking velocimetry (PTV) method is developed for pseudo-2D fluidized beds, utilizing the Voronoi tracking algorithm combined with the relaxation probability tracking algorithm. This method is designed to measure velocities of differently-sized, color-marked particles. Its effectiveness is verified through synthetic images from CFD-DEM simulations, assessing factors like segmentation bias, segmentation ratio, recovery ratio, and error ratio. The color-PTV method demonstrated strong performance in tracking a large number of distinct particles in poly-disperse systems. Additionally, comparisons of experimental results with CFD-DEM simulations using various drag models revealed that simulations incorporating corrections for particle size dispersity showed markedly better alignment with experimental data in terms of mixing index, time-averaged volumetric particle flux, and velocity and granular temperature distributions among particles.
Accuracy and comparison of standard k-ϵ with two variants of k-ω turbulence models in fluvial applications
The paper discusses a new parametric method for aerodynamic optimization of high-speed trains, specifically focusing on reducing train wind effects. It employs a multi-objective particle swarm optimization algorithm to manage various design variables, such as the train’s cross-section, which significantly impacts its aerodynamic performance. The study also introduces a parametrization technique using the NURBS method for more flexible train body profiling. This method allows for a detailed analysis of how changes in the train's design affect its aerodynamics, aiming to optimize the streamlined shape for reduced wind resistance and improved efficiency.
A comprehensive comparison of Two-Fluid Model, Discrete Element Method and experiments for the simulation of single- and multiple-spout fluidized beds
In this study, we use a two-fluid model (TFM) and a computational fluid dynamics-discrete element method (CFD-DEM) approach to analyze the time-averaged hydrodynamics of single- and multiple-spout fluidized beds. The simulations were validated using experimental data from van Buijtenen et al. (2011), incorporating four different interphase drag correlations. The TFM approach includes detailed kinetic theory modeling of granular flows with enhanced particle–wall interactions and an innovative modification of the -rheology to incorporate rolling friction effects. In contrast, the CFD-DEM method integrates rolling friction through an additional torque component. Both methods showed strong agreement in predicting key parameters such as volume fraction, particle velocities, fluxes, and granular temperature, demonstrating the robustness and accuracy of the models in simulating complex fluidized bed dynamics.
Simulation of Flow in Multi-Scale Porous Media Using the Lattice Boltzmann Method on Quadtree Grids
The unified lattice Boltzmann model is enhanced by integrating with quadtree grids to simulate fluid flow in porous media. This model supports multi-scale flow simulation in complex systems and leverages quadtree grids for high-resolution approximation and flexible grid density control. This efficient combination is applied to calculate permeability in various systems, including fractured media, Voronoi tessellations, and computationally generated fractured shale structures. Comparisons with traditional models demonstrate its accuracy and efficiency. Specifically, it effectively distinguishes between matrix and fracture flows in shale, highlighting its utility in analyzing multi-scale porous media.
Efficient implementation of superquadric particles in Discrete Element Method within an open-source framework
The article discusses the development and optimization of particle shape representation in DEM simulations. Traditional DEM models primarily use spherical particles due to their simplicity and computational efficiency. However, real-world applications often involve non-spherical particles, necessitating more complex modeling approaches. This paper introduces superquadric particles, which provide a more accurate representation of various particle shapes in DEM simulations, thus enhancing the model's applicability to real-world scenarios such as industrial processing and materials handling.
Onset of sediment transport in mono- and bidisperse beds under turbulent shear flow
The paper discusses the development and optimization of particle shape representation in DEM simulations. Traditional DEM models primarily use spherical particles due to their simplicity and computational efficiency. However, real-world applications often involve non-spherical particles, necessitating more complex modeling approaches. This paper introduces superquadric particles, which provide a more accurate representation of various particle shapes in DEM simulations, thus enhancing the model's applicability to real-world scenarios such as industrial processing and materials handling.
Calibration of particle interactions for discrete element modeling of powder flow
An experiment using an ASTM B213 standard Hall Flowmeter Funnel was conducted on Ti 6–4 powder particles and simulated via discrete element method in LIGGGHTS. Particle interactions were modeled with a modified Johnson–Kendall–Roberts theory incorporating adhesion based on surface free energy. The simulations used actual particle size distribution data and adjustable parameters like cohesion energy density, restitution coefficient, and dynamic friction were fine-tuned to resemble the experimental particle pile shape. Simulated geometrical properties of the powder pile were measured and compared to experimental outcomes. Local particle size variations within the pile were analyzed, revealing a segregation with larger particles at the top, similar to the Brazil nut effect.
Closure Development for Multi-Scale Fluidized Bed Reactor Models: A Case Study
Chemical looping reforming (CLR) processes highlight significant challenges in chemical engineering, particularly in managing transport limitations. The "NanoSim" project has developed a computational platform to address a wide range of these complexities, including diffusion in solids and nanometer-scale pores, heat and mass transfer between particles and gases, meso-scale clustering, and large-scale dispersion within a reactor. The study reveals that even at the particle scale, considerable uncertainties arise due to the spontaneous formation of meso-scale structures, which affect flow, transport, and reactions. These findings underscore the importance of accounting for these heterogeneities in CLR models to accurately predict reaction rates in industrial-scale reactors.
CFD-DEM simulation of a fluidized bed crystallization reactor
In the present study, a fluidization process in a fluidized bed crystallizer is examined using multiphase CFD-DEM (CFD: Computational Fluid Dynamics; DEM: Discrete Element Method) simulations. The simulations were carried out using the coupled open source software CFDEMcoupling. After validating the simulation results with first experimental measurements, have been used for process understanding and improvement. In particular, regions with complex flow features but important for process outcome have been identified within the crystallizer. Moreover the simulations delivered valuable information that are difficult or even impossible to measure experimentally with sufficient accuracy.
Combining Open Source and Easy Access in the field of DEM and coupled CFD-DEM: LIGGGHTS®, CFDEM® coupling and CFDEM® workbench
The Discrete Element Method (DEM) and its integration with Computational Fluid Dynamics (CFD-DEM) are crucial for designing and optimizing particle processes in various industries. The open-source platforms, CFDEM®coupling and LIGGGHTS®, offer sophisticated simulation capabilities but can be complex to install. The commercial GUI, CFDEM®workbench, simplifies access by combining the advantages of open-source software with an easy setup process. This tool enables broader application of DEM and CFD-DEM modeling in industries like steel, pharmaceuticals, and food production, enhancing the practical utility of these advanced simulation technologies.
Turbulence Budgets in Buoyancy-affected Vertical Backward-facing Step Flow at Low Prandtl Number
This study uses Direct Numerical Simulation to examine the effect of buoyancy on vertical flow over a backward-facing step, particularly with low Prandtl number liquid sodium under mixed convection. It finds that buoyancy reduces recirculation, enhancing heat transfer while varying turbulence effects—decreasing it under moderate conditions and increasing it at high Richardson numbers. The study also analyzes budgets for turbulent kinetic energy, Reynolds shear stress, and heat flux components, highlighting the influence of temperature-pressure gradient correlations. This research aids in understanding liquid metal flows and improving turbulence models for such conditions.
Investigation of wall bounded flows using SPH and the unified semi-analytical wall boundary conditions
This paper examines semi-analytical wall boundary conditions in smoothed particle hydrodynamics (SPH) for fluid flows, focusing on energy conservation and the skew-adjoint property. It reveals that exact energy conservation holds only in continuous SPH, with the discrete form approximating this, resulting in numerical "turbulence." This issue is addressed using a volume diffusion term akin to an approximate Riemann solver. Additionally, enhancements include variable driving force management in periodic flows and generalized Robin-type wall boundary conditions. Numerical experiments validate these advancements, showing significant error reduction and improved handling of free-surface flows, particularly in preventing surface detachment and optimizing interactions at walls.
Highly efficient spatial data filtering in parallel using the opensource library CPPPO
CPPPO is a library developed to facilitate "scale bridging" in multi-scale approaches, integrating parallel data processing routines for both structured and unstructured Eulerian meshes, and Lagrangian data sets. It enables on-the-fly data processing, eliminating the need for storing individual simulation snapshots. Compatible with OpenFOAM®, CPPPO can also interface with other software. The library introduces an advanced parallel data filtering technique that exhibits super-linear scaling on multi-core clusters. Additionally, it offers guidelines for selecting the most effective Eulerian cell selection algorithm based on CPU core count, with demonstrated effectiveness in heat and mass transfer simulations involving dense particle beds.
Heat transfer rates in sheared beds of inertial particles at high Biot numbers
This study investigates heat conduction through sheared granular materials using the ParScale solver and LIGGGHTS discrete element method. Heat transfer to the ambient fluid is modeled with a fixed coefficient, focusing on Biot and Peclet numbers as key parameters for describing heat flux. An analytical solution is provided for calculating mean particle temperature profiles, leading to a continuum model for heat flux developed through extensive simulations. Results show that low Biot numbers align with a simple model assuming uniform particle temperature, whereas higher numbers require accounting for internal temperature gradients to accurately predict heat transfer rates.
Comparing open-source DEM frameworks for simulations of common bulk processes
This study conducts a comparative analysis of nine widely-used, open-source Discrete Element Method (DEM) software frameworks for simulating granular materials. Each framework utilizes explicit time integration, involving contact detection, interaction calculations, and motion equation integration. Significant differences among them include contact models, particle shapes, data analysis methods, data structures, software architecture, parallelization techniques, and user interfaces. The benchmarks, using common bulk processes like silo emptying, drum mixing, and particle impact, employed standard features like spherical particles and the Hertz-Mindlin dry contact model. Scripts for these benchmarks are also provided, facilitating reproducibility and further testing.
A semi-implicit immersed boundary method and its application to viscous mixing
This study addresses challenges in single-phase mixing CFD simulations caused by complex rotating geometries. A parallel semi-implicit immersed boundary method developed in Open∇FOAM for unstructured meshes is introduced. Initially validated through academic test cases, the method was applied to single-phase mixing in both baffled and unbaffled stirred tanks with a pitched blade impeller. The simulation results were benchmarked against experimental data and outcomes from single rotating frame and sliding mesh techniques. The new method demonstrated accuracy comparable to these traditional techniques in predicting flow patterns and torque values, with added ease of application to complex systems featuring multiple overlapping impellers.
An efficient multiple marker front-capturing method for two-phase flows
This study introduces a novel approach for simulating fluid-particle interactions by integrating the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD). The authors employ an immersed boundary method to represent particles within the fluid grid, allowing for accurate modeling of complex interactions. Validation against experimental data demonstrates the model's effectiveness in predicting particle behavior in fluid flows, offering a valuable tool for engineering applications involving particulate systems.
DNS and LES of 3-D wall-bounded turbulence using Smoothed Particle Hydrodynamics
Smoothed Particle Hydrodynamics (SPH) has expanded its application to include real-world engineering scenarios, particularly in simulating turbulent three-dimensional flows. This paper highlights a significant gap in the investigation of such flows, as most SPH studies focus on the decay of isotropic turbulence without solid wall influences. The study conducts two sets of SPH simulations on turbulent channel flows. The first, a quasi-direct numerical simulation (DNS) in a reduced-size channel, tests SPH's capability as a Navier–Stokes solver without turbulence models, successfully reproducing turbulent statistics except near the wall. The second set, a large eddy simulation (LES) in a standard size channel, fails to accurately predict turbulent statistics, with failures linked to inadequate velocity-pressure interaction handling by SPH’s collocated and large stencil discretization.
Numerical and experimental analysis of the extraction mechanism of an anchor plate embedded in saturated sand
Floating offshore structures often use submerged anchor plates for foundational support, requiring understanding of their extraction resistance under various conditions. Throughout their lifecycle, these foundations face complex loading from waves, tidal currents, and wind. Notably, when extracting these anchors at lifecycle’s end, their resistance significantly exceeds the combined forces of self-weight, hydrostatic, and earth pressures due to a vacuum effect as the anchor moves and increases the volume underneath, drawing in pore water. An experimental model-scale study measured pore pressures and soil movements using particle image velocimetry (PIV), exploring different extraction velocities. Additionally, numerical simulations using unresolved coupled CFD-DEM methods validated these experimental findings, enhancing understanding of anchor extraction dynamics.
DNS of Turbulent Bubbly Downflow with a Coupled Level-Set/Volume-of-Fluid Method
Turbulent flows containing bubbles or droplets play a critical role in both industrial applications and natural processes, such as in bubble column reactors, spray combustion systems, and rain clouds. Understanding the interactions between these bubbles or droplets and the turbulent flow around them is challenging, especially when these particles are of finite size relative to the Kolmogorov scale and are present in concentrations beyond dilute conditions. The complexity of these interactions remains a significant area of research due to its implications on the efficiency and effectiveness of various systems involving multiphase flows.
Buoyancy Effects on Turbulent Heat Transfer Behind a Backward-Facing Step in Liquid Metal Flow
Heat transfer is one the most important technical applications in fluid mechanics. Heat transfer behind sudden changes of the cross section such as a backward-facing step flow is particularly important in many devices such as the in- and outflow of thermal storage containers, collectors of power conversion systems, as well as highly heat loaded surfaces like those in concentrated solar power (CSP) plants, to name but a few examples.
CFD–DEM study of residence time, droplet deposition, and collision velocity for a binary particle mixture in a Wurster fluidized bed coater
The article delves into optimizing the drying process of pharmaceutical powders using fluidized bed drying technology. It focuses on examining various parameters such as air flow rate, temperature, and particle characteristics to enhance the efficiency and uniformity of the drying process. This study is critical for improving product quality and reducing production costs in the pharmaceutical industry, where moisture content and particle integrity are crucial.
Influence of various DEM shape representation methods on packing and shearing of granular assemblies
This paper examines how different shape representation methods influence the bulk response of granular assemblies in Discrete Element Method simulations, focusing on angle-of-repose and direct-shear tests. It considers three rolling resistance models for spherical particles and uses superquadrics and multi-spheres to model non-spherical particles like cuboids and cylinders. The study presents detailed results on how shape affects granular behavior, including comparisons of various methods. Findings from angle-of-repose tests indicate that rolling friction models effectively capture the avalanching characteristics of cube-like and cylindrical particles. Direct-shear test results highlight that only the elasto-plastic rolling resistance model accurately predicts shear strength and dilative response, although not porosity, of non-spherical particles. This research helps pinpoint optimal shape-description parameters for different representation methods.
A semi-analytical model for the effective thermal conductivity of a multi-component polydisperse granular bed
A theoretical model to predict the effective thermal conductivity of a multi-component polydisperse granular bed is presented. A simple energy balance analysis is used to arrive at an approximate analytical expression for the effective thermal conductivity. Simulation of heat transfer in a granular bed is carried out using an open source Discrete Element Method (DEM) package called LIGGGHTS. The derived analytical expressions for the effective thermal conductivity compares well with the results obtained from DEM simulations for granular beds comprising of different components with different sizes.
A viscoelastic bonded particle model to predict rheology and mechanical properties of hydrogel spheres
The study introduces a numerical simulation tool based on the Discrete Element Method tailored for predicting the behavior of hydrogel spheres, extensively used in various sectors due to their adaptable mechanical properties. Initially, the model's accuracy is assessed through an oscillatory compression test on a single hydrogel, achieving a close match with experimental rheological properties; the relative errors for the normal modified storage and loss moduli (E’ and E”) are about 3% and 11%, respectively. This approach, utilizing bonded particles and a viscoelastic constitutive relation, is validated further with a particle-particle compression test, showing promising alignment with experimental contact forces. This model's adaptability makes it suitable for a broad range of applications.
Detection and Visualization of Splat and Antisplat Events in Turbulent Flows
The study introduces the first Lagrangian method for identifying splat and antisplat events in three-dimensional turbulent flows, where splats occur when fluid impinges on a surface, transferring energy from normal to tangential velocity components, and antisplats represent the reverse. This method employs strain tensors on flow-embedded flat surfaces to detect these events across various scales. Validated using artificial flow fields, the method was applied to analyze turbulent flow over a backward-facing step from direct numerical simulations. Results confirm the method's efficacy and reliability in identifying these events in complex flows, marking it as a valuable tool for analyzing turbulent flow dynamics.
Extended CFD–DEM for free‐surface flow with multi‐size granules
The study enhances CFD-DEM modeling with the Volume of Fluid (VOF) method to simulate free-surface flows, integrating fluid dynamics on coarse grids with particle dynamics. This approach uses an advection equation to manage liquid phase fraction and enables volume replacement between fluid and particles. A novel "porous sphere" technique allows larger particle use without losing fluid grid resolution. Validations across scenarios like dam breaks and particle sedimentation confirm the effectiveness of the new solver, cfdemSolverVOF, even with a reduced size ratio between fluid cells and particle diameter, enhancing its suitability for dynamic geotechnical applications with diverse particle sizes.
Buoyancy-affected backward-facing step flow with heat transfer at low Prandtl number
This paper explores turbulent upward flow of liquid metal in a vertical channel with a heated backward-facing step, pertinent to solar power plants. Direct numerical simulations assess the buoyancy effects by comparing scenarios with and without the buoyancy term, featuring a Richardson number of 0.338. The results show that buoyancy significantly alters the flow, reducing recirculation and enhancing heat transfer at the heated wall due to increased temperature advection. Detailed analysis of turbulent heat fluxes demonstrates how buoyancy modifies flow conditions. These insights help improve the physical understanding and modeling of turbulent heat transfer at low Prandtl numbers.
Direct numerical simulation of turbulent bubbly down flow using an efficient CLSVOF method
This study uses Direct Numerical Simulations (DNS) to explore how bubbles affect turbulence in downward-flowing vertical channels. With a Reynolds number of 180, simulations are carried out for two void fractions, analyzing three bubble sizes using the Coupled Level-Set/Volume-of-Fluid (CLSVOF) method. Efficiency improvements are made with a fast pressure-correction method, allowing FFT-based solutions. Validation shows excellent accuracy, with a significant speedup of 22 times by the new solver. Results indicate bubble accumulation in the channel core, altering the mean velocity profile and reducing velocity fluctuations near the walls, while enhancing turbulence in the core. Larger bubbles increase dissipation, amplifying turbulent kinetic energy centrally.
Investigating mixing and segregation using discrete element modelling (DEM) in the Freeman FT4 rheometer
The study utilizes the Discrete Element Method (DEM) to examine mixing and segregation dynamics in a Freeman FT4 powder rheometer with binary particle mixtures, focusing on varying particle size ratios and volume fractions. It finds that larger particle sizes or greater volume fractions of large particles accelerate segregation through a sifting mechanism, enhanced by higher particle velocities. Segregation intensifies radially from the center to the outer layer. Additionally, the study notes that segregation and mixing energies are influenced by frictional parameters. The FT4 rheometer's potential is highlighted for evaluating particulate materials' segregation tendencies by measuring flow energy gradients post-mixing cycles, aiding in optimizing blending operations in industrial settings.
Review and future options for computer modelling in the sugar industry
This paper provides a review of computer modeling applications in the sugar industry over the past 25 years, highlighting both successes and challenges. It notes that while advancements in hardware and software have enhanced modeling capabilities, certain processes like cane cleaning, billet preparation, and sugar drying have seen limited improvement due to the computational intensity required to model numerous particle interactions. Despite these challenges, progress has been made in understanding these complex systems. The paper suggests employing robust commercial software with customizable subroutines or leveraging open-source software capable of utilizing large parallel computing resources to overcome computational barriers. It discusses software options that could potentially enhance efficiency and design within the industry.
Thermo-hydraulic flow in a sudden expansion
The article explores enhancements in DEM simulations by incorporating superquadric particles. These particles offer a more realistic representation of varied particle shapes, which is crucial for applications like materials processing and handling. This advancement allows for the simulation of complex particle interactions more accurately than traditional spherical models.
Transition between free, mixed and forced convection
The study investigates optimal conditions for producing charcoal from coconut shells, focusing on temperature and residence time's effects on charcoal yield. It includes a detailed experimental setup using a pyrolysis reactor and discusses the thermal conversion of the shells, highlighting the relationship between process parameters and the efficiency of charcoal production.
Direct Minimization of the least-squares spectral element functional – Part I: Direct solver
The paper presents a method for solving the Helmholtz equation using spectral element methods. The authors propose a direct minimization approach to obtain the least-squares solution, aiming to improve computational efficiency and accuracy in solving this fundamental equation in physics and engineering.
Extension of a CLSVOF method for droplet-laden flows with a coalescence/breakup model
The CLSVOF method for droplet-laden flows now includes a model for droplet coalescence and breakup, enhancing its realism. This method uses unique marker functions for each droplet to avoid numerical coalescence seen in traditional methods. Coalescence is determined by a film drainage model, which activates when contact time exceeds a set threshold, merging droplet markers. Breakup is modeled by splitting these markers. Validated by simulations at various Weber numbers
Development of an unresolved CFD–DEM model for the flow of viscous suspensions and its application to solid–liquid mixing
Viscous solid-liquid mixing, crucial in industries, is often studied in turbulent regimes, but challenges persist in laminar and transitional flows. This paper discusses using multiphase CFD to examine such mixings, especially the unresolved CFD-DEM method that combines fluid dynamics with discrete element modeling to simulate large quantities of particles accurately. This study extends the method to viscous flows, exploring various momentum coupling strategies and introducing a sub-grid viscosity model to maintain correct suspension rheology. The model is applied to a stirred tank with a pitched blade turbine, and validated both qualitatively and quantitatively against experimental data, demonstrating its effectiveness in predicting particle suspension behaviors.
Physical and scale-by-scale analysis of Rayleigh–Bénard convection
The article presents a novel approach to studying turbulent Rayleigh–Bénard convection (RBC) in a compound physical/scale space domain. It utilizes data from direct numerical simulations conducted in a laterally unbounded domain confined between two horizontal walls, exploring cases with a Prandtl number of 0.7 and Rayleigh numbers ranging from 1.7×10^5 to 1.0×10^7. This study offers insights into the dynamics and scale interactions within turbulent RBC, contributing valuable understanding to the field of fluid dynamics.
Resolved and subgrid dynamics of Rayleigh–Bénard convection
This work introduces a theoretical framework for analyzing thermally driven turbulence, extending classical equations to accommodate inhomogeneous and anisotropic flows. It utilizes scale-by-scale budget equations for velocity and temperature structure functions, identifying two critical scales that delineate quasi-homogeneous and inhomogeneity-dominated ranges. Applied to large-eddy simulation, it assesses filtering effects on Rayleigh–Bénard convection dynamics. Results indicate that classic eddy-viscosity models may be inadequate for large filter lengths, suggesting alternative subgrid closures are needed. This framework offers a valuable tool for evaluating subgrid-scale models in simulations of turbulent flows.
Effects of Contact Force Model and Size Distribution on Microsized Granular Packing
The article discusses the importance of contact force models in the accurate simulation and understanding of mechanical systems where contact occurs, such as in manufacturing processes. The study analyzes different models for their effectiveness in predicting the behavior of systems at various scales, particularly focusing on the scalability and applicability of these models in real-world scenarios. This research is crucial for advancing precision in manufacturing techniques and improving the design and efficiency of mechanical assemblies and tools.
What are the microscopic events of colloidal membrane fouling?
This study employs CFD-DEM simulations to analyze colloidal membrane fouling within a microfluidic system that simulates a porous microfiltration membrane. It focuses on how colloidal particles overcome energy barriers for adsorption and desorption, both between particles and with membrane surfaces. Key insights include the transition of particle interactions from the secondary to the primary minimum of the DLVO potential and the behaviors of adsorbed particles, such as re-entrainment or downstream gliding, often occurring in clusters. The pore geometry within the membrane notably influences fouling patterns. These findings lay groundwork for further exploration of the dynamics between hydrodynamic forces and surface energy effects in colloidal filtration.
Fully-resolved simulations of particle-laden viscoelastic fluids using an immersed boundary method
This study introduces a direct simulation code developed to analyze the dynamics of solid spheres in viscoelastic fluids, utilizing an open-source finite-volume solver enhanced by an immersed boundary method. This solver is designed to handle fully-resolved simulations and employs a log-conformation tensor to manage issues at high Weissenberg numbers effectively. Benchmark tests include sphere sedimentation in viscoelastic and Newtonian fluids, rotation in shear flows, and cross-stream migration in Poiseuille flow, with results validated against experimental and computational references. Additionally, the solver's accuracy in capturing phenomena like the Segré–Silberberg effect and shear-induced particle alignment was demonstrated, showing the influence of fluid rheology and confinement on particle dynamics.
Space and time behaviour of the temperature second-order structure function in Rayleigh-Bénard convection
The article discusses the flow structure of an under-expanded supersonic impinging (USI) jet, where the flow exits from the nozzle at a Mach number of 1 and impinges on a wall placed vertically above the nozzle. The study models the behavior and interactions at different distances, specifically focusing on a distance of five times the nozzle diameter (z/d = 5). This setup is used to observe the dynamic effects and flow patterns that result when the supersonic jet impacts the impingement surface, which is crucial for applications in aerospace and other industries requiring precise control of jet behaviors.
Modeling of wheel–soil interaction over rough terrain using the discrete element method
A numerical study utilizing the Discrete Element Method (DEM) examined the effects of rough terrain on the mobility and efficiency of small unmanned ground vehicles. The DEM simulations, validated against single-wheel test data involving straight-line motion and wheel-digging on flat soil, showed good qualitative agreement. In tests on 20 sinusoidal rough terrain profiles, mobility generally decreased, with drawbar pull dropping by up to 15% and driving torque increasing by up to 35% due to terrain-induced oscillations. The experiments used a slow speed and soft lunar regolith simulant, which minimized vertical accelerations and vehicle vibrations, thereby reducing performance impacts.
Simulation von Förderprozessen bei Vibrationsförderanlagen
The paper discusses the achievable conveying speeds of vibratory conveyors and their dependency on the motion function of the conveyor mechanism. It emphasizes the need for targeted simulation of these systems using the discrete element method (DEM), necessitating the application of geometrically networked conveyor replicas with practice-relevant motion functions to accurately model and optimize vibratory conveying processes.
Simulation der peristaltischen Förderung von Stückgütern als Schüttgut
The article introduces a novel conveying principle designed to resiliently handle and transport bulk package structures. This system utilizes a flexible composite surface made up of small-scale conveyor modules, which exhibit peristaltic properties to quickly resolve package jams and allow controlled handling of sub-quantities to achieve necessary throughput in material flow systems. This concept effectively combines principles of bulk and unit load conveying for transporting packages as bulk material. The basic functionality of the conveyor concept is validated through numerical simulations using the Discrete Element Method and multibody simulation.
Single Particle Growth, Fragmentation and Morphology Modelling: A DEM Approach
The paper discusses the synthesis and characterization of polyacrolein using radical polymerization methods. Optimal conditions for acrolein polymerization are achieved using I4 as an initiator at a ratio of 1:50 to the monomer, with a monomer concentration of 7.5 mol L^-1, a reaction temperature of 50 °C, and a duration of 6 hours. Under these conditions, the yield of polyacrolein can reach up to 93.76%. The polymers formed are further characterized to confirm their structure and properties, which is essential for their potential application in various industrial fields.
Stochastic simulation of the Uplift process for the Irish Electricity Market
In the Irish electricity market participants declare their true marginal costs and therefore the Shadow Price alone does not guarantee that generators will recover their fixed running costs. The so-called uplift complements the price and ensures that the generators recover their total costs. The aim of this paper is to review purely stochastic features of the uplift and make an attempt to simulate a new process reconstructing the original data characteristics. We propose two alternative algorithms basing on the uplift wait-jump structure as well as daily and annual seasonality. Presented results show that this kind of reconstruction is possible up to a quantitatively comparable degree.
Direct Numerical Simulation of turbulent heat transfer behind a backward‐facing step at low Prandtl number
The paper presents Direct Numerical Simulations of the turbulent flow of a low Prandtl number fluid over a backward‐facing step with heat transfer. The backward‐facing step flow is investigated as a generic configuration for sudden changes in cross section. Several simulations are reported: for isothermal conditions, for heat transfer with the Prandtl number of air, and for heat transfer with the Prandtl number of liquid sodium. The simulation for air is compared to results from literature. The differences induced by reduction of the Prandtl number are then assessed by comparison of the two cases. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of isotropic and anisotropic subgrid scale models in Large Eddy Simulations of a backward‐facing step and square duct flow
The present paper employs the anisotropic explicit algebraic subgrid‐stress model (EASM), proposed by Marstorp et al., developed in the spirit of an earlier explicit algebraic RANS‐model for statistical closures. The EASM in its elementary, computationally efficient non‐dynamic version is used for Large Eddy Simulation of three‐dimensional flows over a backward‐facing step at a bulk Reynolds number of 4805 and a square duct at 2205. Its performance is assessed by comparison with experimental data and an own Direct Numerical Simulation. Furthermore, a set of eddy‐viscosity models, including the recent σ‐model, is employed for comparison. Various statistical quantities are evaluated to assess the respective performance of the different models showing, that the anisotropic EASM compares favorably to the other models.
Heated vertical duct flow of liquid metal with and without expansion
The effects of buoyancy on vertical duct flows with one heated side wall are investigated by means of Direct Numerical Simulations. In particular, the flow through square ducts and behind the expansion of a backward‐facing step with side walls are presented for the forced and mixed convection regime. These configurations allow studying the interaction of buoyancy forces with secondary flow of second kind in the square duct and with the shear layer and recirculation zone in case of the expansion. In both configurations, buoyancy substantially alters the mean flow field, the turbulent stresses, and the heat transfer compared to the corresponding forced convection cases.
A Modified Statistical Interparticle Collision Model For Colliding Particle Clouds
In this paper, a modified stochastical interparticle collision model is discussed and valdiated. A channel flow with a constriction serves as a test case. The simulation of the thereby colliding particle strands clearly shows that without the collision sub–model, the simulation with the standard Lagrangian model yields unreasonable results. After adding the stochastical collision sub–model, the Lagrangian model is able to describe the flow situation if the mass load is not too high.
Influence of rolling friction on single spout fluidized bed simulation
This study introduces a novel approach to simulate the behavior of dense particle suspensions in fluid flows. By integrating the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD), the model effectively captures particle-particle and particle-fluid interactions. Validation against experimental data demonstrates its accuracy in predicting flow patterns and particle distribution, offering a valuable tool for analyzing complex multiphase flows in engineering applications.
Predictions of the P1 approximation for radiative heat transfer in heterogeneous granular media
The P1 approximation, a simplified model for thermal radiation, is integrated into a combined CFD-DEM framework to enhance computational efficiency while handling dependent scattering and coarse-graining effects. Analysis using analytical solutions shows good agreement for steady-state and transient behaviors in size-disperse systems, though heat flux predictions exhibit unphysical oscillations due to temperature discrepancies at sharp changes in solid fraction. To address this, two solutions—smoothing radiative properties and introducing pseudo-scattering—are proposed. The framework supports extensive coarse-graining, tested up to a million times the particle size. Comparisons with experimental data from a pebbled bed in vacuum and nitrogen environments show that the model closely replicates observed trends, maintaining a relative temperature error under 10%.
Discrete particle simulation of radial segregation in horizontally rotating drum: Effects of drum-length and non-rotating end-plates
DEM simulations explore the radial segregation of two different-sized grains in a horizontal rotating drum, focusing on the impact of drum length and grain-end-plate friction. Findings reveal that longer drums exhibit higher segregation ratios, with end-plate friction having minimal impact. Conversely, in shorter drums, segregation is slow or negligible, but reducing end-plate friction enhances segregation. Increasing friction beyond inter-grain and grain-wall friction decreases segregation in longer drums and promotes mixing in shorter ones. This behavior is attributed to diffusion caused by shearing strain from rougher end-plates, which raises granular temperature and leads to mixing instead of segregation.
Spherical shock-wave propagation in three-dimensional granular packings
The article investigates the spherical shock-wave propagation in an open dense granular packing. This is studied by examining the sudden expansion of a spherical intruder within the packing. The focus is on the correlation between the geometrical structure of the granular fabric and the properties of the shock-wave as it propagates through the medium. This research is crucial for understanding the mechanical behavior of granular materials under dynamic loading, which has implications in various engineering and scientific applications.
A Novel Modeling Approach for Plastics Melting within a CFD-DEM Framework
This study introduces a novel three-dimensional modeling approach for single-screw extrusion that integrates the feed and melt sections of the process, which were traditionally considered separately. The new model, implemented within the CFDEMCoupling® framework, combines Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM) with a pioneering melting model to simulate the phase transition from solid to liquid. To validate this model, a melting apparatus was constructed and operationalized. Simulations were performed to calculate melting rates and compared with experimental outcomes, showing good alignment. This successful integration suggests the feasibility of joint CFD-DEM simulations for single-screw extruders, offering a more comprehensive analysis of the extrusion process.
Application of a hybrid Lattice Boltzmann–Finite Volume turbulence model to cyclone short-cut flow
This study investigates the solubility and micronization of phenacetin using supercritical carbon dioxide. The solubility was measured at pressures from 9.0 to 30.0 MPa and temperatures between 308.0 K and 328.0 K, revealing a mole fraction solubility up to 10⁻⁵. Four density-based semi-empirical models were applied to correlate the experimental data, with the Adachi-Lu-modified Chrastil model showing the best agreement. The Rapid Expansion of Supercritical Solution (RESS) process was employed to produce fine phenacetin particles, with parameters such as extraction temperature, pressure, nozzle temperature, diameter, and collection distance influencing particle size and morphology.
Regimes of liquid transport through sheared beds of inertial smooth particles
This article investigates liquid transport in moving particle beds, focusing on transfer during particle collisions and convective transport due to particle motion. Simplistic models typically handle these processes, but this study evaluates various models across different flows, ultimately selecting one for detailed shear flow simulations with soft, frictional spheres. Results from these simulations help create regime maps for effective liquid flux and draw parallels to thermal energy transport, confirming the models' accuracy. These findings aim to develop continuum models for describing liquid and thermal transport through granular materials, providing a foundation for future research.
Hybrid parallelization of the LIGGGHTS open-source DEM code
This work presents our efforts to implement an MPI/OpenMP hybrid parallelization of the LIGGGHTS open-source software package for Discrete Element Methods (DEM). We outline the problems encountered and the solutions implemented to achieve scalable performance using both parallelization models. Three case studies, including two real-world applications with up to 1.5 million particles, were evaluated and demonstrate the practicality of this approach. In these examples, better load balancing and reduced MPI communication led to speed increases of up to 44% compared to MPI-only simulations.
Identification of DEM simulation parameters by Artificial Neural Networks and bulk experiments
This study presents a method to identify DEM simulation parameters using artificial neural networks, linking macroscopic results with microscopic parameters. An ANN is trained with varying DEM parameters to predict material behaviors, creating a database that correlates micro-level parameters with macro behaviors. This approach simplifies parameter identification for non-cohesive granular materials, requiring only one training session per experiment set to establish a generic link between experimental results and DEM parameters.
DEM study of mechanical characteristics of multi-spherical and superquadric particles at micro and macro scales
This study examines the mechanical characteristics of cubical particles using Multi-spheres and Superquadrics in DEM simulations via EDEM and LIGGGHTS. Initial single particle tests assess impact, interlocking, sliding, and tilting, highlighting the importance of surface bumpiness and edge sharpness. Subsequent bulk simulations include angle of repose, Jenike shear, and silo flow tests. Results demonstrate that particle shape descriptors significantly influence bulk behavior, particularly heap profiles and shear strength in dense packings. While shape features less affect flow patterns and mass flow rates in silo discharge, they crucially impact stress distribution, underscoring the importance of accurate particle modeling in DEM studies.
Modeling of non-spherical particle flows: Movement and orientation behavior
This work introduces a novel approach for calculating drag forces and torques on non-spherical particles in liquid media, addressing the technical challenges in processing particles with unconventional morphologies like fibers or flakes. Current tools fall short in predicting behaviors of these particulate systems, especially when considering particle-particle interactions and orientation, leading to costly and prolonged process development. The proposed method, integrating CFD-DEM coupling, employs Stokesian Dynamics to compute drag forces and torques, utilizing the multi-sphere method to represent non-spherical particles. This tool aims to enhance process design and understanding of non-spherical particulate systems.
A hybrid tabulation-scaling implementation of Thornton and Ning's plastic–adhesive particle contact theory
This paper introduces two novel implementations of the Thornton and Ning (TN) plastic-adhesive particle contact theory within the framework of the Discrete Element Method (DEM). Unlike the original TN method that uses an indirect and incremental calculation, the new approaches include a Newton-Raphson bisection (NRB) methodology for exact non-incremental contact force calculations, and a tabulation-scaling (TS) implementation that approximates the elastic-adhesive unloading curve, significantly enhancing computational speed. The TS method replicates the energy transfer of elastic-adhesive unloading within 3% of the NRB results. Using real material parameters like Young's modulus and adhesion energy, the TS approach is both physically accurate and computationally efficient. These implementations are compatible with the open-source DEM software, LIGGGHTS, facilitating broader application in simulating the behavior of plastic-adhesive particles.
Investigation of screening performance of banana screens using LIGGGHTS DEM solver
In this numerical work, natural convection of CuO–water nanofluid and pure water in a cavity submitted to different heating modes on its vertical walls, is analyzed using the Lattice Boltzmann Method (LBM). The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. The influence of pertinent parameters such as Rayleigh number (Ra = 103–106), Hartmann number (Ha = 0–80), heat generation or absorption coefficient (q = − 10, − 5, 0, 5, 10) and nanoparticle volume concentration (ϕ = 0–0.04) on the flow and heat transfer characteristics has been examined. In general, by considering the role of Brownian motion, the enhancement in heat transfer is observed at any Hartman and Rayleigh numbers. In addition, the heat generation or absorption influences the heat transfer in the cavity at Ra = 103 more than other Rayleigh numbers as the least effect is observed at Ra = 106.
Numerical study and experimental validation of particle strand formation
The study investigates the pneumatic conveying of spherical glass particles through a rectangular channel. A double-looping mechanism is introduced to generate a particle strand at the channel's bottom. Particle Image Velocimetry (PIV) measures particle velocity and volume concentration profiles, while numerical simulations employ the Discrete Phase Model in Fluent software. Additional sub-models address particle-wall and particle-particle collisions, as well as particle rotation effects.
Effects of nanoparticles Brownian motion in a linearly/sinusoidally heated cavity with MHD natural convection in the presence of uniform heat generation/absorption
This study uses the Lattice Boltzmann Method (LBM) to analyze natural convection of CuO-water nanofluid and pure water within a differently heated cavity. It employs the KKL correlation for determining the nanofluid's effective thermal conductivity and viscosity. The effects of various parameters such as Rayleigh number (Ra = 10^3 to 10^6), Hartmann number (Ha = 0 to 80), heat generation/absorption coefficient (q = -10 to 10), and nanoparticle volume concentration (ϕ = 0 to 0.04) on flow and heat transfer are explored. Results show enhanced heat transfer due to Brownian motion across all tested Hartmann and Rayleigh numbers, with heat generation or absorption impacting heat transfer most significantly at the lowest Rayleigh number (Ra = 10^3).
Regimes of subsonic compressible flow in gas-particle systems
This study introduces regime maps for subsonic flow in dense gas-particle systems, distinguishing between compressible and effectively incompressible flow areas. These maps are valuable for guiding researchers and industry professionals in selecting modeling techniques and verifying numerical solvers. The findings challenge the traditional compressibility threshold of Mach 0.3, showing significant compressible effects in porous media flows even at lower Mach numbers (
Coupled CFD–DEM simulation of fluid–particle interaction in geomechanics
Jet-milling is a particle engineering process widely adopted in industrial manufacturing to reduce the particle size of powders. Computational Fluid Dynamics simulations (CFD) coupled with Discrete Element Modelling (DEM) proved to be a valuable tool to tackle the complexity and the non-linearity of particle breakage and classification occurring in mills. To date however, they have been employed to address only single aspects of process design being unable to reproduce it completely. The coupled CFD-DEM simulations presented in this work are for the first time capable of simultaneously describe particle fragmentation, particle-gas interaction and classification. Through coarse-graining, realistic amounts of powder can be simulated allowing to demonstrate/study how the hold-up mass slows down the milling gas affecting classification and thus the milling performance. Bottlenecks/limitations of model and methodology are critically examined to understand what is currently preventing us from creating a digital twin of the milling process.
4-way coupling CFD-DEM simulation of particle breakage and classification in a spiral jet mill: A critical analysis
This paper explores the advancement of Computational Fluid Dynamics (CFD) coupled with Discrete Element Modeling (DEM) in simulating jet-milling processes, crucial for reducing particle sizes in industrial manufacturing. Traditionally, CFD-DEM has addressed only specific aspects of milling due to its complexity. For the first time, this study integrates particle fragmentation, particle-gas interaction, and classification in a single simulation, enhancing process design comprehensiveness. Through coarse-graining techniques, the simulation manages realistic powder volumes, revealing how mass hold-up decelerates milling gas, impacting classification and overall milling efficiency. The study also identifies current limitations in modeling, crucial for progressing towards a fully-functional digital twin of the milling process.
A modified cohesion model for CFD–DEM simulations of fluidization
CFD-DEM simulations analyzed gas-fluidization in particles with van der Waals cohesion for Group A and Group C particles. The study revealed that using lower spring constants in simulations, compared to real-world values, affects flow patterns. A modified cohesion model, validated through two-particle collision analysis, showed that for Group A particles, bubble size distribution remained consistent regardless of stiffness, while Group C particles maintained stable flow patterns unless stiffness was extremely low. The model effectively handled mildly cohesive Group A particles but was less accurate for strongly cohesive Group C particles, where large agglomerates formed, confirming earlier findings by Kobayashi et al. (2013).
Coarse Graining for Large-scale DEM Simulations of Particle Flow – An Investigation on Contact and Cohesion Models
This paper builds on previous research to evaluate the scalability of the linear spring dashpot (LSD) contact law through shear test box simulations with Lees-Edwards boundary conditions. The study expands to compare the LSD model with the Hertz contact model and briefly explores the Johnson-Kendall-Roberts (JKR) cohesive contact model. Results indicate that the Hertz model behaves similarly to the scaled LSD model in both inertial and quasi-static regimes. For coarse-graining scenarios, both models maintain nearly constant stress levels in the quasi-static regime, whereas stress significantly increases in the inertial regime. The paper also provides preliminary findings on the JKR model.
Parallel open source CFD-DEM for resolved particle-fluid interaction
This paper presents a parallelized resolved method for simulating immersed body dynamics in fluids using the Fictitious Domain Method (FDM). The approach couples the Lagrangian Discrete Element Method (DEM) for body tracking with Computational Fluid Dynamics (CFD) for fluid flow and pressure calculation. The algorithm alternates between CFD calculations, body velocity inclusion, and force corrections to ensure conservation equations are met. Dynamic local mesh refinement minimizes fluid cells near bodies. Integrated into the CFDEMcoupling framework, combining LIGGGHTS and OpenFOAM®, the parallelization enables large-scale simulations. Validation includes flow around settling and rotating spheres, and studies of the Boycott effect.
Towards fast parallel CFD-DEM: An open-source perspective
This paper introduces "LammpsFoam," a coupled CFD-DEM solver combining LAMMPS for discrete element modeling and OpenFOAM® for fluid dynamics. Building on previous work coupling EDEM and FLUENT, this new solver overcomes the limitations of shared memory systems by enabling parallel simulations on distributed memory machines using MPI. The approach accounts for volume displacement, particle drag, and Magnus force, making it suitable for a wide range of particle-fluid systems. The paper outlines the modeling strategy, validates the solver with a test case, and provides an outlook for future applications in handling computationally intensive industrial problems.
An open source CFD-DEM perspective
This paper introduces a coupled solver combining the Discrete Element Method (DEM) for granular material behavior, using LIGGGHTS, and Computational Fluid Dynamics (CFD) for interstitial fluid flow, using OpenFOAM®. Designed for large-scale industrial problems, the solver supports fully parallel simulations on distributed memory machines via MPI. This integration enables efficient handling of computationally intensive problems. Validation through test cases demonstrates accurate predictions of pressure drop and minimum fluidization velocity, showcasing the solver's capability for realistic industrial applications.
The birth of a dinosaur footprint: Subsurface 3D motion reconstruction and discrete element simulation reveal track ontogeny
This study reconstructs 3D foot movements of guineafowl walking on granular substrates using biplanar X-rays and integrates the data into discrete element method (DEM) simulations. The combination reveals how foot motion causes sediment deformation both at the surface and subsurface "virtual bedding planes," exposing organized subsurface tracks despite surface collapse. The longest toe penetrates ~5 cm at a 30° angle before slipping backward on withdrawal. These insights uncover how track features form through localized deformations, termed "track ontogeny," offering a mechanistic link between limb motion, substrate dynamics, and track morphology, enhancing fossil track interpretation and understanding of deformable substrate locomotion.
Comprehensive DEM-DPM-CFD simulations-model synthesis, experimental validation and scalability
This study combines the Discrete Element Method (DEM) for granular material behavior with a finite volume Computational Fluid Dynamics (CFD) model for interstitial fluid flow. To reduce computational costs, DEM is complemented by the Discrete Phase Model (DPM) for dispersed granular flow using spatial domain decomposition, enabling both models to operate within a single simulation. The implementation supports fully parallel simulations for all three models. The approach's efficiency and accuracy are validated through three examples, and its scalability is discussed, highlighting its suitability for large-scale coupled fluid-granular flow simulations.
Describing the Drying and Solidification Behavior of Single Suspension Droplets Using a Novel Unresolved CFD-DEM Simulation Approach
This study introduces an unresolved CFD-DEM simulation approach to model the drying and solidification of single suspension droplets in a spray dryer. Solidification begins when a critical solid concentration is reached at the droplet surface, forming bonds between primary particles. Drying conditions are derived from large-scale spray dryer simulations for different droplet sizes. Results show that higher drying rates promote hollow particle formation when solidification occurs early. The findings help identify optimal spray dryer operating conditions to achieve desired particle morphologies, advancing simulation-based process and product design for spray-dried products.
Towards efficient simulation of off-gas scrubbing by a hybrid Eulerian Lagrangian model
This research presents a hybrid Eulerian–Lagrangian model for simulating wet scrubbers used in capturing fine dust particles from off-gas streams. The model traces representative droplets in a Lagrangian manner while treating dust as passive Eulerian phases. It also incorporates a wall film model that solves shallow water equations, accounting for droplet deposition, film separation, and stripping. Numerical results for pressure drop and capturing efficiency align well with experimental measurements, indicating the model's effectiveness in simulating the scrubbing process.
Models, algorithms and validation for opensource DEM and CFD-DEM
This study presents a versatile framework for simulating coupled fluid-granular systems using the Discrete Element Method (DEM) for particle motion and Computational Fluid Dynamics (CFD) for interstitial fluid flow. It details two coupling approaches: unresolved CFD-DEM and resolved CFD-DEM with an Immersed Boundary (IB) method. Both methods are validated against analytical solutions and experimental data, demonstrating their effectiveness in modeling complex fluid-particle interactions.
Multi-scale Analysis of Turbulent Rayleigh-Bénard Convection
This study presents results from a direct numerical simulation of turbulent Rayleigh-Bénard convection at a Rayleigh number of RaRa and Prandtl number of 0.7. The flow is dominated by coherent thermal plumes, localized regions of fluid with a temperature contrast. Using the wall-parallel divergence of the velocity field, two key near-wall events are identified: plume impingement and ejection. Impingement leads to the formation of larger structures in velocity and temperature fields, suggesting a reverse energy transfer from small to large scales in the near-wall region, challenging the classical turbulence picture of energy cascading from large to small scales.
Towards an Improved Subgrid-Scale Model for Thermally Driven Flows
This study investigates the effect of spectral cutoff filtering on the resolved and subgrid dynamics of turbulent Rayleigh–Bénard convection (RBC) using Direct Numerical Simulation (DNS) data. For small filter lengths, resolved processes closely match exact dynamics, with reduced dissipation balanced by subgrid-scale sinks. At larger filter lengths, resolved dynamics near walls deplete, and subgrid-scale behavior becomes more complex, deviating from purely dissipative effects. The findings suggest that conventional eddy-viscosity and diffusivity models used in large-eddy simulations may fail for large filters, highlighting the need for alternative closure models to accurately capture subgrid-scale effects in RBC systems.
Simulation Partikelbeladener Strömungen: Diskrete, Kontinuierliche Und Hybride Modellierungsansätze
Prozesse der Pulvermetallurgie basieren auf einer großen Anzahl kleiner (meist polydisperser), fester Partikel. In einigen Prozessschritten (Pulvervorbehandlung, Formfüllen) lässt sich das makroskopische Pulververhalten durch einen Strömungszustand beschreiben, der durch eine zusätzlich vorhandene Gasphase beeinflusst werden kann. Basierend auf einem illustrativen Beispiel einer Pulverentmischung in einer bi-dispersen Wirbelschicht werden kontinuierliche und diskrete state-of-the-art-Simulationsmodelle präsentiert und deren individuelle Stärken und Limitationen diskutiert. Schließlich wird ein Ausblick auf neue, hybride Modellierungskonzepte gegeben, um komplexe Pulverströmungen abbilden zu können. Der Vortrag schließt mit der Vorstellung einer gemeinschaftlichen, internationalen Plattform für die Entwicklung von Simulationswerkzeugen für partikelbeladene Strömungen.
Sediment erosion a numerical and experimental study
A new numerical model to describe the erosion process in the presence of a free surface flow is proposed and tested against experimental data. The fluid flow is captured by a Computational Fluid Dynamics (CFD) method, whereas the sediment is modelled at a grain size level using Discrete Element Method (DEM). The fluid-particle interaction is realized by a coupling of CFD and DEM, capturing the physics of sediment erosion and deposition at a very detailed particle-scale level.With the aid of optical and acoustic measurement techniques (PIV,ADV) the fluid flow as well as turbulence downstream of a weir is investigated experimentally. Using a LASER based measuring device local bed erosion downstream of the hydraulic structure is analysed and compared to numerical results. It is shown that for numerical simulations different turbulence models are able to capture the global flow pattern but have significant influence on predicted erosion rates. The numerical model presented in this paper is completely realized in an open source environment.
State of the art in mapping schemes for dilute and dense Euler-Lagrange simulations
This study presents enhanced Euler-Lagrange (EL) simulations for gas-particle flows using robust Lagrangian-to-Euler mapping schemes. By integrating field smoothing techniques from Pirker et al. (2011) and Capecelatro and Desjardins (2013), the new schemes support implicit, explicit, and hybrid time marching, enabling simulations of highly loaded flows with broad particle size distributions. Performance is demonstrated across three cases: (i) a bubbling bi-disperse fluidized bed, (ii) freely sedimenting suspension, and (iii) particle injection in a turbulent cross-flow. The results highlight the schemes' accuracy and versatility for complex gas-particle flow systems in academic and industrial applications.
Thermofluidic compression effects to achieve combustion in a low-compression scramjet engine
This study investigates thermofluidic compression effects in scramjet inlets using Reynolds-averaged Navier–Stokes simulations. A simplified scramjet engine with insufficient inlet compression was tested, featuring a wide rectangular combustor and a central hydrogen injector. Higher fuel equivalence ratios (0.22, 0.17, 0.13) led to earlier ignition and faster combustion, driven by local compression from the increased mass flow rate. Supplementary helium injections confirmed this effect. The higher mass flow generated stronger injector bow shocks, compressing the free-stream gas, increasing OH radical production, and promoting ignition. Subsequent heat release provided thermal compression, boosting downstream pressure, temperature, and overall combustion efficiency.
Correction to: Thermofluidic compression effects to achieve combustion in a low-compression scramjet engine
This study examines the role of thermofluidic compression in scramjet inlets, using Reynolds-averaged Navier–Stokes simulations. A simplified scramjet engine with low inlet compression was analyzed, featuring a wide rectangular combustor and central hydrogen injector. Increasing the fuel injection mass flow rate (equivalence ratios of 0.22, 0.17, and 0.13) led to earlier ignition and faster combustion due to local compression. Stronger injector bow shocks compressed the free-stream gas, enhancing OH radical production and ignition. Heat release from combustion further provided thermal compression, boosting downstream pressure, temperature, and combustion efficiency, demonstrating that fuel injection can compensate for insufficient inlet compression.
Parallel Resolved Open Source CFD-DEM: Method, Validation and Application
In the following paper the authors present a fully parallelized Open Source method for calculating the interaction of immersed bodies and surrounding fluid. A combination of computational fluid dynamics (CFD) and a discrete element method (DEM) accounts for the physics of both the fluid and the particles. The objects considered are relatively big compared to the cells of the fluid mesh, i.e. they cover several cells each. Thus this fictitious domain method (FDM) is called resolved. The implementation is realized within the Open Source framework CFDEMcOupling ( www.cfdem.com ), which provides an interface between OpenFOAM® based CFD-solvers and the DEM software LIGGGHTS ( www.liggghts.com ). While both LIGGGHTS and OpenFOAM® were already parallelized, only a recent improvement of the algorithm permits the fully parallel computation of resolved problems. Alongside with a detailed description of the method, its implementation and recent improvements, a number of application and validation examples is presented in the scope of this paper.
Coupled LBM–DEM Micro-scale Simulations of Cohesive Particle Erosion Due to Shear Flows
This paper investigates the erodibility of cohesive micro-scale particles under varying surface shear stresses using a coupled lattice Boltzmann method (LBM) and discrete element method (DEM). Compacted layers of 100 cohesive spheres are subjected to shear flow, revealing a critical shear stress threshold for erosion. Beyond this threshold, the erosion rate increases linearly with excess surface shear stress. Additionally, an upward motion mechanism for detached particles is observed. The study highlights the potential of the LBM-DEM approach for modeling dynamic erosion processes in three dimensions, offering insights into fluid-particle interactions in cohesive particle systems.
Laboratory Tests and Numerical Simulations of Mixing Superheated Virgin Aggregate with Reclaimed Asphalt Pavement Materials
This study examines the heating and binder transfer of reclaimed asphalt pavement (RAP) during mixing with superheated virgin aggregate, focusing on factors affecting blending efficiency. Laboratory tests and Discrete Element Method (DEM) simulations were conducted to analyze temperature evolution and RAP binder transfer in a drum mixer. Results showed that longer mixing times or higher virgin aggregate temperatures are required for high RAP content or high RAP moisture. DEM simulations proved effective for studying the mixing process and can be used in the future to optimize production processes for RAP mixes, improving sustainability without compromising pavement performance.
Combined experimental and numerical approach for wear prediction in feed pipes
This study combines experimental and numerical approaches to investigate erosive wear in feed pipes. Lab-scale tests revealed that erosion rates depend on material properties and impact angles: steel experiences more wear at higher impact angles, while rubber is more affected at lower angles. Empirical erosion models fail to capture material-dependent critical impact energies and fatigue effects. A CFD-DEM approach was used to simulate particulate flow in pipes, and long-term wear measurements tracked wear progression. While further validation is required, the results show promising potential for accurate erosion prediction, enhancing understanding of wear processes in industrial applications.
Plastic Accumulation in Front of a Plate in Cross Flow: Model Scale Test and CFD-DEM Modelling
This study presents results from flume experiments and CFD-DEM simulations of plastic accumulation in front of a fixed plate, simulating ocean cleanup systems. Experiments examined flow velocity, plate draft (Froude number), and three plastic particle types, observing accumulation profiles under increasing loads. A linear relationship between relative accumulation depth and plate Froude number was identified for specific particle types. The open-source CFDEM® code, coupling LIGGGHTS® and OpenFOAM®, successfully reproduced the experimental results. Limitations of the experimental setup and single-phase CFD-DEM approach were discussed, highlighting the need for further calibration and research to improve accuracy and applicability.
Supplemental Proceedings: Materials Fabrication, Properties, Characterization, and Modeling
The "TMS 2011 Annual Meeting Supplemental Proceedings, Volume 2: Materials Fabrication, Properties, Characterization, and Modeling" compiles research presented at the 2011 TMS Annual Meeting and Exhibition. This volume encompasses studies on materials fabrication techniques, property analysis, characterization methods, and modeling approaches, offering insights into advancements in materials science and engineering.
Discrete Element Method Modeling of Laser Beam Absorption on Rough Surfaces and Powder Beds
The energy transfer from a laser beam source to material surfaces with arbitrary geometrical features and variable surface roughness is the crucial step in many high-end engineering applications. We present a high-fidelity numerical framework for the simulation of laser beam interaction with such surfaces, which include meshed geometry of arbitrary shape and material Lagrangian particles. The method discretizes the laser source as a collection of photon-type immaterial Lagrangian particles and is able to capture the effects of multiple reflections, angle-dependent reflectivity, and polarization change. Validation is conducted against the experimental measurement of the effective reflectivity of a rough copper sample, revealing the impact of the polarization effects. The method is also applied to powder beds and powder layers, and a new theoretical algebraic model for the effective reflectivity of powder layers versus layer sparseness is proposed, based on the simulation data.
DEM-PM Contact Model with Multi-Step Tangential Contact Displacement History
This study provides an overview of the Discrete Element Method (DEM) for granular flow and geomechanics, focusing on the Penalty Method (PM) for soft-body contacts. A new multi-time-step tangential contact displacement history model is introduced and validated through direct shear tests using the Chrono DEM solver. Comparisons with models lacking tangential history show significant under-prediction of shear stress by a factor of ten. Results from Chrono agree well with experiments on glass spheres and simulations from LIGGGHTS. The study confirms the model's accuracy in replicating physical geomechanical tests, highlighting its effectiveness in capturing realistic shear behavior in granular materials.
Simulation of fluid suspended particle behaviour subject to transverse standing acoustic fields
This computational study examines the effectiveness of standing wave acoustic fields for deflecting quartz particles in water through a vertically oriented parallelepiped duct (50×50×70 cm³). Using OpenFOAM (CFD), LIGGGHTS (DEM), and CFDEM coupling, the model simulates drag, buoyancy, gravity, and acoustic forces in idealized conditions. Particles (5–30 μm) were carried at flow speeds of 0.1, 0.5, and 1 m/s while subject to acoustic forces at two frequencies (14,794 Hz and 26,629 Hz). Results show frequency influences deflection efficiency, nodal distribution, and particle residence time. The model demonstrates qualitative agreement with theoretical trends, validating its applicability for particle deflection studies.
CFD-DEM on Multiple Scales - An Extensive Investigation of Particle-Fluid Interactions
This thesis focuses on simulating particle-laden flows using coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). Resolved CFD-DEM, applied for detailed analysis of a few large particles, involved developing a parallelized Fictitious Domain Method (FDM), validated through examples like Boycott’s blood cell settling case. For large particle systems, unresolved CFD-DEM analyzed blast air-induced cavities (raceways) in blast furnaces. A pseudo-2D lab model provided experimental validation, revealing 2D effects. This led to 3D simulations of a full-scale blast furnace. The tools and solvers developed were integrated into the Open Source CFDEMproject, advancing methods for both resolved and unresolved particle-laden flows.
Modeling proppant flow in fractures using LIGGGHTS, a scalable granular simulator
This study uses a Discrete Element Method (DEM) model to simulate proppant flowback in fractures under confining pressures, analyzing fracture width, confining stress, flow velocity, and proppant cohesion. Results reveal three regimes: full fracture evacuation at high flow rates and low stress, fully packed fractures at high stress, and partially evacuated fractures in intermediate conditions. Proppant production depends on cohesion, while fracture width is influenced by stress and flow velocity. A controlled, gradual well flowback rate, adjusted for leak-off coefficient, is recommended to stabilize the proppant pack and reduce costly flow restrictions and equipment damage.
A computational framework for coupled modelling of three-phase systems with soluble surfactants
This study presents a comprehensive CFD-DEM modeling framework for bubble-particle interaction in the presence of soluble surfactants, relevant for industrial processes like froth flotation. The framework couples OpenFOAM (CFD) and LIGGGHTS (DEM) via CFDEM, incorporating gas-liquid-solid momentum coupling and the Volume of Fluid (VOF) method for bubble surface dynamics. Particle-interface forces are modeled as hyperbolic functions of phase fraction gradients, including DLVO, non-DLVO, and inertial forces. Soluble surfactant effects are represented through a volumetric transport equation for interfacial tension. The model is modular, mass-conservative, and extensible for future developments, offering a significant advancement in flotation system simulations.
Modeling of Laser Beam Absorption on Rough Surfaces, Powder Beds and Sparse Powder Layers
This study introduces two models to predict energy transfer from a laser beam to surfaces with arbitrary geometry and variable roughness. The first is a high-fidelity numerical framework using the Discrete Element Method (DEM) to simulate photon-particle interactions, accounting for multiple reflections, angle-dependent reflectivity, and polarization changes. Validation against rough copper surfaces highlights the significance of polarization effects. The second model is a phenomenological correlation for predicting effective reflectivity of sparse powder layers, such as recondensed metal vapor in laser welding. The correlation aligns well with simulation results and experimental data, offering tools for diverse laser-material interaction scenarios.