Computational Fluid Dynamics-Discrete Element Method is used to model gas-solid systems in several applications in energy,pharmaceutical and petrochemical industries.Computational performance bot-tlenecks often limit ...Computational Fluid Dynamics-Discrete Element Method is used to model gas-solid systems in several applications in energy,pharmaceutical and petrochemical industries.Computational performance bot-tlenecks often limit the problem sizes that can be simulated at industrial scale.The data structures used to store several millions of particles in such large-scale simulations have a large memory footprint that does not fit into the processor cache hierarchies on current high-performance-computing platforms,leading to reduced computational performance.This paper specifically addresses this aspect of memory access bottlenecks in industrial scale simulations.The use of space-flling curves to improve memory access patterns is described and their impact on computational performance is quantified in both shared and distributed memory parallelization paradigms.The Morton space flling curve applied to uniform grids and k-dimensional tree partitions are used to reorder the particle data-structure thus improving spatial and temporal locality in memory.The performance impact of these techniques when applied to two benchmark problems,namely the homogeneous-cooling-system and a fluidized-bed,are presented.These optimization techniques lead to approximately two-fold performance improvement in particle focused operations such as neighbor-list creation and data-exchange,with~1.5 times overall improvement in a fluidization simulation with 1.27 million particles.展开更多
The n-body instability is investigated with the soft-sphere discrete element method.The divergence of nearby trajectories is quantifed by the dynamical memory time.Using the inverse proportionality between the dynamic...The n-body instability is investigated with the soft-sphere discrete element method.The divergence of nearby trajectories is quantifed by the dynamical memory time.Using the inverse proportionality between the dynamical memory time and the largest Lyapunov exponent,the soft-sphere discrete ele-ment method results are compared to previous hard-sphere molecular dynamics data for the first time.Good agreement is observed at low concentrations and the degree of instability is shown to increase asymptotically with increasing spring sifness.At particle concentrations above 30%,the soft-sphere Lya-punov exponents increase faster than the corresponding hard-sphere data.This paper concludes with a demonstration of how this case study may be used in conjunction with regression testing and code verification activities.展开更多
An unknown in coupled Eulerian-Lagrangian models for particle flow,such as CFD-DEM,which has received fairly little attention in the literature to date is the size of the filter width in the transfer kernel.This work ...An unknown in coupled Eulerian-Lagrangian models for particle flow,such as CFD-DEM,which has received fairly little attention in the literature to date is the size of the filter width in the transfer kernel.This work provides a preliminary glimpse at how this parameter can influence the solution in cold-flow,unbounded fluidization.Comparison to previously published direct numerical simulation data is used to suggest an appropriate range for this parameter.展开更多
文摘Computational Fluid Dynamics-Discrete Element Method is used to model gas-solid systems in several applications in energy,pharmaceutical and petrochemical industries.Computational performance bot-tlenecks often limit the problem sizes that can be simulated at industrial scale.The data structures used to store several millions of particles in such large-scale simulations have a large memory footprint that does not fit into the processor cache hierarchies on current high-performance-computing platforms,leading to reduced computational performance.This paper specifically addresses this aspect of memory access bottlenecks in industrial scale simulations.The use of space-flling curves to improve memory access patterns is described and their impact on computational performance is quantified in both shared and distributed memory parallelization paradigms.The Morton space flling curve applied to uniform grids and k-dimensional tree partitions are used to reorder the particle data-structure thus improving spatial and temporal locality in memory.The performance impact of these techniques when applied to two benchmark problems,namely the homogeneous-cooling-system and a fluidized-bed,are presented.These optimization techniques lead to approximately two-fold performance improvement in particle focused operations such as neighbor-list creation and data-exchange,with~1.5 times overall improvement in a fluidization simulation with 1.27 million particles.
文摘The n-body instability is investigated with the soft-sphere discrete element method.The divergence of nearby trajectories is quantifed by the dynamical memory time.Using the inverse proportionality between the dynamical memory time and the largest Lyapunov exponent,the soft-sphere discrete ele-ment method results are compared to previous hard-sphere molecular dynamics data for the first time.Good agreement is observed at low concentrations and the degree of instability is shown to increase asymptotically with increasing spring sifness.At particle concentrations above 30%,the soft-sphere Lya-punov exponents increase faster than the corresponding hard-sphere data.This paper concludes with a demonstration of how this case study may be used in conjunction with regression testing and code verification activities.
文摘An unknown in coupled Eulerian-Lagrangian models for particle flow,such as CFD-DEM,which has received fairly little attention in the literature to date is the size of the filter width in the transfer kernel.This work provides a preliminary glimpse at how this parameter can influence the solution in cold-flow,unbounded fluidization.Comparison to previously published direct numerical simulation data is used to suggest an appropriate range for this parameter.
