Near Continuum Gas Flows

Abstract

In this paper, two near continuum gas flow problems are studied. The problem of near continuum gas flows over a cylinder is investigated numerically. Three types of boundary conditions for the cylinder surface are adopted; 1).non-slip and constant temperature surface; 2).velocity slip with a consideration of velocity gradient, and temperature jump at the surface; and 3).velocity slip with considerations of both velocity and temperature gradients, along with temperature jump at the surface. Two-dimensional Navier-Stokes equations for compressible flows are adopted with the Roe numerical scheme. The numerical results include flowfield properties, coefficient distributions for surface pressure, friction, heat flux, velocity slip, temperature jump and total drag. The third type of surface boundary conditions do not create significant differences from the second type. Rarefication Effects on the total drag are also investigated. The second problem is the near planar stagnation point flow with velocity-slip and temperature-jump boundary conditions. Exact analytical solutions for the temperature distributions are obtained. It is found that with the near continuum boundary conditions, the gas at the surface is hotter while the heat flux to the surface is smaller.