Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

An immersed boundary method with direct forcing for the simulation of particulate flows

The Maxwell-Stefan approach to mass transfer

Discrete particle simulation of particulate systems: A review of major applications and findings

Sir: We appreciate Professor Albright’s interest in our work (Simpson et al., 1996). His letter makes one valid criticism of our analysis of the product distribution and raises many insupportable concerns which can be traced to his assumption that the product distribution and dominant pathways in zeolite-catalyzed alkylation should be the same as those for the sulfuric acid-catalyzed reaction. We disagree with Professor Albright on his claim that our kinetic analysis is flawed. We respond below to each of the points raised by him.

Rebuttal to the Comments of Lyle F. Albright on “Kinetic Analysis of Isobutane/Butene Alkylations over Ultrastable H−Y Zeolite”

Fine grid resolution is necessary to fully demonstrate the accuracy of two-fluid model(TFM)in predicting gas-solids flows in the riser section of circulating beds.Insufficient grid resolutions will likely lead to incorrect solutions.In most industrial applications involving large devices,it is impractical to use fine grids,and therefore,constitutive models that are suitable for the coarse-grid TFM simulations are required.It has been reported in some literatures that microscopic drag laws,such as those due to Gibilaro and Gidaspow,did not yield grid-independent solutions over the range of grid sizes investigated in some test problems.Filtered two-fluid models were developed using the results of highly resolved simulations.A filtering procedure was applied to the results of these simulations to deduce the constitutive models for the residual correlations appearing in the corresponding filtered TFM equations.These equations were appropriate for coarse-grid simulations of gas-particle flows.Using the same example studied by Mckeen and Pugsley(2003),it was first demonstrated that grid-independent predictions could be afforded by a filtered TFM,in which filtered drag and particle phase stress models were included.Then grid-independent and experimentally consistent solutions could also be obtained with filtered TFM model when filtered particle phase stress model was replaced with kinetic theory model as long as filtered fluid-particle drag force model was used.

Grid-independence of sub-grid filtered two-fluid models

uidparticle drag force and the stability of the uniformly uidized state

Abstract Lattice-Boltzmann simulations of fluid flow through sheared assemblies of monodisperse spherical particles have been performed. The friction coefficient tensor extracted from these simulations is found to become progressively more anisotropic with increasing Péclet number, $Pe= \\dot {\\gamma } {d}^{2} / D$ , where $\\dot {\\gamma } $ is the shear rate, $d$ is the particle diameter, and $D$ is the particle self-diffusivity. A model is presented for the anisotropic friction coefficient, and the model constants are related to changes in the particle microstructure. Linear stability analysis of the two-fluid model equations including the anisotropic drag force model developed in the present study reveals that the uniformly fluidized state of low Reynolds number suspensions is most unstable to mixed mode disturbances that take the form of vertically travelling waves having both vertical and transverse structures. As the Stokes number increases, the transverse-to-vertical wavenumber ratio decreases towards zero; i.e. the transverse structure becomes progressively less prominent. Fully nonlinear two-fluid model simulations of moderate to high Stokes number suspensions reveal that the anisotropic drag model leads to coarser gas–particle flow structures than the isotropic drag model.

Sankaran Sundaresan

Papers

Rebuttal to the Comments of Lyle F. Albright on “Kinetic Analysis of Isobutane/Butene Alkylations over Ultrastable H−Y Zeolite”

Grid-independence of sub-grid filtered two-fluid models

uidparticle drag force and the stability of the uniformly uidized state

Effect of microstructural anisotropy on the fluid-particle drag force

Traveling waves in multi-phase flows