Dynamic multi-scale structures in a gas-solid suspension with 1024 particles are investigated with direct numerical simulations using macro-scaleparticle methods. The suspension is found to be characterized by hetero...
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Dynamic multi-scale structures in a gas-solid suspension with 1024 particles are investigated with direct numerical simulations using macro-scaleparticle methods. The suspension is found to be characterized by heterogeneity with clustering solids and bypassing gas. The solid particle velocity distribution is found to be anisotropic though nearly Maxwellian in each direction, which is in agreement with measurements in liquid-solid systems, supporting the necessity of incorporating anisotropy into the continuum descriptions of such flows. The drag force on the particles in the dilute phase can be far larger than that in the center of the dense phase, and much less than that on the phase interface, suggesting the insufficiency of correlating interphase friction to local averaged voidage only. However, statistics shows nearly Gaussian distribution of the drag forces, which is potentially favorable to establishing a diffusion model accounting for drag dispersion. The need for a multi-scale description of gas-solid flows, and on the other hand, the power of particle methods as exploring tools for this purpose, are demonstrated. (c) 2006 Elsevier Ltd. All rights reserved.
As a particle method, macro-scale pseudo-particle modeling (MaPPM) is an effective approach applied to micro-scale simulation of particle-fluid systems. In this paper, a parallel algorithm for macro-scalepseudo-parti...
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As a particle method, macro-scale pseudo-particle modeling (MaPPM) is an effective approach applied to micro-scale simulation of particle-fluid systems. In this paper, a parallel algorithm for macro-scale pseudo-particle modeling based on spatial decomposition (SD) is presented. The parallel implementation utilizes MPI as the programming environment. Due to movement of particles during simulation, the parallelization of MaPPM may suffer from load imbalance and attendant performance degradation. Recursive Coordinate Bisection (RCB) is adopted to partition the whole computational domain in a dynamic fashion to balance the workload in processors. The Shift scheme is modified to meet the communication requirement in the dynamic partition. The parallel approach was applied to simulation of bubble behavior in gas-solid fluidized beds with different system sizes to test its performance. The computations were conducted on cluster of workstations (COW). Experimental results show that the algorithm has a good scalability. With dynamic load balancing (DLB), the parallel efficiency can be improved by up to 8%. To sum up, it was a successful implementation for the parallelization of macro-scale pseudo-particle modeling. (c) 2004 Elsevier Ltd. All rights reserved.
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