Subsonic flow boundary conditions for the direct simulation Monte Carlo method

Abstract

The performance of different types of boundary conditions used in direct simulation Monte Carlo models of subsonic flows for single species flow fields is assessed in this study. An inlet boundary condition that permits the specification of pressure and temperature is investigated, as well as one that permits the specification of mass flow rate and temperature. A new inlet boundary condition is suggested that permits the total mass flow rate to be specified without requiring inter-processor communication during a parallel computation. Two types of outlet boundary conditions are investigated, one in which the outlet pressure is maintained by controlling the porosity of the outlet surface, and another in which particles are introduced at the outlet with properties such that the desired pressure is maintained. Each of the boundary conditions investigated produce flow field results for a single species, microchannel flow that are in good agreement with an analytical solution of the flow field and previously reported results. However, a simulation of a more complicated multi-species flow inside a vapor deposition reactor shows that some of the predicted flow field and surface properties are a function of the type of outlet boundary condition used.