In this research,a Graphical Processing Unit(GPU)accelerated Discrete Element Method(DEM)code was developed and coupled with the Computational Fluid Dynamic(CFD)software MFiX to simulate granular and multiphase flows ...In this research,a Graphical Processing Unit(GPU)accelerated Discrete Element Method(DEM)code was developed and coupled with the Computational Fluid Dynamic(CFD)software MFiX to simulate granular and multiphase flows with heat transfers and chemical reactions.The Fortran-based CFD solver was coupled with the CUDA/C++based DEM solver through inter-process pipes.The speedup to the CPU version of MFiX-DEM is about 130-243 folds in the simulation of particle packings.In fluidized bed simulations,the DEM computation time is reduced from 91%to 17%with a speedup of 78 folds.The simulation of Geldart A particle fluidization revealed a similar level of importance of both fluid and particle coarse-graining.The filtered drag derived from the two-fluid model is suitable for Euler-Lagrangian simulations with both fluid and particle coarse-graining.It overcorrects the influence of sub-grid structures if used for simulations with only fluid coarse-graining.展开更多
This article presents the development and validation of the Superquadric Discrete Element Method(SuperDEM)for non-spherical particle simulation using a superquadric particle method in open-source CFD suite MFiX.A supe...This article presents the development and validation of the Superquadric Discrete Element Method(SuperDEM)for non-spherical particle simulation using a superquadric particle method in open-source CFD suite MFiX.A superquadric particle-particle contact algorithm with accelerating and stabilizing strategy was developed.A superquadric particle-arbitrary wall contact algorithm was developed,which enables the simulation in complex geometry.The solver was validated by comparing with experimental data generated in this study or available in the literature.Tests include cylinder contacting with a wall,static packing of M&M chocolate candies in a cylindrical container,static packing of cylinders in a cylindrical container,dynamic angle of repose of cylinders in a rotating drum,and discharging of chocolate candies from a hopper.Besides,MPI parallelization of the solver was implemented and the parallel performance of the solver using MPI was assessed through large-scale simulations of 1 million,10 million,and 100 million particles on up to 6800 cores,which demonstrates that the SuperDEM solver has great potential for industrial-scale systems simulation.展开更多
Numerical simulations of gas-solid fluidized beds based on the kinetic theory of granular flow exhibit a significant dependence on domain discretization. Bubble formation, bubble size and shape all vary greatly with t...Numerical simulations of gas-solid fluidized beds based on the kinetic theory of granular flow exhibit a significant dependence on domain discretization. Bubble formation, bubble size and shape all vary greatly with the discretization, and the use of an inappropriate scale resolution leads to inaccurate predictions of fluidization hydrodynamics. In this study, grid-independent solutions of the two fluid model were examined by comparing the bed expansions obtained from numerical simulations with experimental results and empirical predictions, based on bubbling fluidized beds of Geldart B particles. Grid indepen- dence was achieved with a grid resolution equal to 18 times the particle diameter. The simulation results were compared with previously published data for verification purposes. The results of this work should provide a guideline for choosing the appropriate grid size and thereby minimize the time and expense associated with large simulations.展开更多
A two-fluid model based on the kinetic theory of granular flow for the rapid-flow regime and the Coulomb friction law for the quasi-static regime is applied to predict the hydrodynamics of dense gas-particle flow in a...A two-fluid model based on the kinetic theory of granular flow for the rapid-flow regime and the Coulomb friction law for the quasi-static regime is applied to predict the hydrodynamics of dense gas-particle flow in a three-dimensional fluidized bed. Two different models for the particle stress tensor that use different constitutive equations in the elastic-inertial regime are examined to assess their ability to predict bed dynamics. To understand how particle stress models affect structural features of the flow, a quantitative analysis is performed on some important aspects of the mechanics of bubbling beds that have received relatively little attention in the literature. Accordingly, different flow regimes are identified in the context of fluidized beds through the dimensionless inertial number, and the main characteristics of each regime are discussed. In addition, how the particle stress tensor manifests itself in the bubble characteristics, natural frequency of the bed, and particle Reynolds stress are investigated, all of which help to better understand the complex dynamics of the fluidized bed. The numerical results are validated against pub- lished experimental data and demonstrate the significant role of the stress tensor in the elastic-inertial regime.展开更多
Polysiloxane coatings on yttria stabilized zirconia(YSZ)microspheres of 500μm were simulated in a spout fluidized bed coater using Multiphase Flow with Interface Exchange-Discrete Element Modelling(MFiX-DEM).Two diff...Polysiloxane coatings on yttria stabilized zirconia(YSZ)microspheres of 500μm were simulated in a spout fluidized bed coater using Multiphase Flow with Interface Exchange-Discrete Element Modelling(MFiX-DEM).Two different coater configurations were developed to study the influence of gas velocity and its distribution on particle dynamics.The presence of the Wurster tube not only enhances the dis-tribution but also increases the overall residence time of the particles.Investigations were also carried out with different Wurster tube positions(normal,10%and 20%lowered from its initial position).Among these,20%lowered Wurster tube position demonstrated the most effective coating process.The effects of gas inlet pressure on the average gas velocity and the distribution of particles were analyzed.More than 97%of the particles can be retained.The derived results,including average gas velocity,particle retention percentage,and distribution of particles with gas velocity,are being used to guide the experimental work in obtaining defect-free coatings for YSZ microspheres.展开更多
文摘In this research,a Graphical Processing Unit(GPU)accelerated Discrete Element Method(DEM)code was developed and coupled with the Computational Fluid Dynamic(CFD)software MFiX to simulate granular and multiphase flows with heat transfers and chemical reactions.The Fortran-based CFD solver was coupled with the CUDA/C++based DEM solver through inter-process pipes.The speedup to the CPU version of MFiX-DEM is about 130-243 folds in the simulation of particle packings.In fluidized bed simulations,the DEM computation time is reduced from 91%to 17%with a speedup of 78 folds.The simulation of Geldart A particle fluidization revealed a similar level of importance of both fluid and particle coarse-graining.The filtered drag derived from the two-fluid model is suitable for Euler-Lagrangian simulations with both fluid and particle coarse-graining.It overcorrects the influence of sub-grid structures if used for simulations with only fluid coarse-graining.
文摘This article presents the development and validation of the Superquadric Discrete Element Method(SuperDEM)for non-spherical particle simulation using a superquadric particle method in open-source CFD suite MFiX.A superquadric particle-particle contact algorithm with accelerating and stabilizing strategy was developed.A superquadric particle-arbitrary wall contact algorithm was developed,which enables the simulation in complex geometry.The solver was validated by comparing with experimental data generated in this study or available in the literature.Tests include cylinder contacting with a wall,static packing of M&M chocolate candies in a cylindrical container,static packing of cylinders in a cylindrical container,dynamic angle of repose of cylinders in a rotating drum,and discharging of chocolate candies from a hopper.Besides,MPI parallelization of the solver was implemented and the parallel performance of the solver using MPI was assessed through large-scale simulations of 1 million,10 million,and 100 million particles on up to 6800 cores,which demonstrates that the SuperDEM solver has great potential for industrial-scale systems simulation.
文摘Numerical simulations of gas-solid fluidized beds based on the kinetic theory of granular flow exhibit a significant dependence on domain discretization. Bubble formation, bubble size and shape all vary greatly with the discretization, and the use of an inappropriate scale resolution leads to inaccurate predictions of fluidization hydrodynamics. In this study, grid-independent solutions of the two fluid model were examined by comparing the bed expansions obtained from numerical simulations with experimental results and empirical predictions, based on bubbling fluidized beds of Geldart B particles. Grid indepen- dence was achieved with a grid resolution equal to 18 times the particle diameter. The simulation results were compared with previously published data for verification purposes. The results of this work should provide a guideline for choosing the appropriate grid size and thereby minimize the time and expense associated with large simulations.
文摘A two-fluid model based on the kinetic theory of granular flow for the rapid-flow regime and the Coulomb friction law for the quasi-static regime is applied to predict the hydrodynamics of dense gas-particle flow in a three-dimensional fluidized bed. Two different models for the particle stress tensor that use different constitutive equations in the elastic-inertial regime are examined to assess their ability to predict bed dynamics. To understand how particle stress models affect structural features of the flow, a quantitative analysis is performed on some important aspects of the mechanics of bubbling beds that have received relatively little attention in the literature. Accordingly, different flow regimes are identified in the context of fluidized beds through the dimensionless inertial number, and the main characteristics of each regime are discussed. In addition, how the particle stress tensor manifests itself in the bubble characteristics, natural frequency of the bed, and particle Reynolds stress are investigated, all of which help to better understand the complex dynamics of the fluidized bed. The numerical results are validated against pub- lished experimental data and demonstrate the significant role of the stress tensor in the elastic-inertial regime.
基金supported by the Office of Nuclear Energy of Department of Energy(grant No.DE-NE0008807).
文摘Polysiloxane coatings on yttria stabilized zirconia(YSZ)microspheres of 500μm were simulated in a spout fluidized bed coater using Multiphase Flow with Interface Exchange-Discrete Element Modelling(MFiX-DEM).Two different coater configurations were developed to study the influence of gas velocity and its distribution on particle dynamics.The presence of the Wurster tube not only enhances the dis-tribution but also increases the overall residence time of the particles.Investigations were also carried out with different Wurster tube positions(normal,10%and 20%lowered from its initial position).Among these,20%lowered Wurster tube position demonstrated the most effective coating process.The effects of gas inlet pressure on the average gas velocity and the distribution of particles were analyzed.More than 97%of the particles can be retained.The derived results,including average gas velocity,particle retention percentage,and distribution of particles with gas velocity,are being used to guide the experimental work in obtaining defect-free coatings for YSZ microspheres.
