Rarefied Compressible Two-Dimensional Jet Flows

Abstract

Rarefied jet flows expanding into vacuum or impinging onto a flat plate have many important applications, e.g. space propulsion, materials processing, and interactions between rocket plume and lunar ground. In this paper, we investigate rarefied jet gas flows out of a two-dimensional slit. The first part concentrates on the problem of collisionless gas flows expanding into vacuum, while the second part on rarefied jet flows impinging onto a flat plate which is set vertically to the plume flow direction. With a relation between velocity-directions and geometry- positions, we obtain the corresponding analytical density and velocity distributions in front of the slit; For the second problem, this study provides near-plate density, slip velocity, temperature, pressure and shear stress on location very close or right on the flat plate. Numerical simulation results obtained with the direct simulation Monte Carlo method validate most of the analytical solutions. In general, the comparisons between the complex exact analytical solutions and the numerical results are virtually identical. The same procedure developed in this paper is applicable to study many other rarefied jet flow problems.