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

Studies in char gasification—III: The combustion zone

The problem of the optimal distribution of two different catalysts in a nonisothermal packed bed reactor is analyzed. State variable constraints, such as maximum allowable temperature, may be incorporated through a penalty function approach into the steepest ascent solution of this problem. Loading a wall-cooled reactor with two chemically different catalysts is compared to dilution of a single catalyst with inerts for temperature moderation. A criterion is presented for estimating whether catalyst dilution may be necessary in order to keep reactor temperature below some maximum allowable value. Conditions for optimal loading with a two-dimensional reactor model are presented and applied to catalyst dilution in a butane oxidation reactor. Suboptimal catalyst loadings are compared with the optimal loading.

Optimal catalyst distribution and dilution in nonisothermal packed bed reactors

Time-dependent vertical gas—liquid flow in packed beds

A crossflow model for pulsing flow in a trickle bed of large cross section is presented. The trickle bed is idealized as being made up of pulses and the trickling flow region surrounding these pulses. Assuming the macroscopic gas flow around the pulses to be irrotational and the pulses to contain only liquid, the model equations are derived. An analysis of the model and comparison with the experimental results of Christensen (1986) reveals that the irrotational flow model underestimates the pulse velocity for realistic pulse shapes. This can be attributed to the underestimation by the model of the drag exerted by the trickling region on the pulses. By dropping the irrotational flow assumption and viewing the model as semiempirical, a single parameter characterizing the magnitude of this drag is estimated from the pulse velocity data. When this estimated value for this parameter is employed, the model predicts the average pressure gradient data reasonably well.

Mathematical modeling of pulsing flow in large trickle beds

The dynamics of carbon combustion is studied. It is shwon that the carbon particle will not ignite if the furnace temperature is below a certain critical value. In addition, carbon particles display thermal instabilities which can be delayed or eliminated by increasing the water vapor concentration and/or the furnance temperature.

Sankaran Sundaresan

Papers

Studies in char gasification—III: The combustion zone

Optimal catalyst distribution and dilution in nonisothermal packed bed reactors

Time-dependent vertical gas—liquid flow in packed beds

Mathematical modeling of pulsing flow in large trickle beds

Diffusion and reaction in a stagnant boundary layer about a carbon particle, part 7: Transient behavior and effect of water vapor