Monte Carlo simulations of hypersonic flows past blunt bodies

Abstract

This paper reports on the steps taken to develop a gas-kinetic simulation of hypersonic flows past the nose region of re-entry vehicles. For the validation of both the direct simulation Monte Carlo (DSMC) and the molecular dynamics (MD) methods, the Oseen vortex decay problem was chosen to emphasize the conservation of angular momentum. Furthermore, an analytical solution of the Navier-Stokes equation exists for this problem. The results obtained with both methods correlate well with the analytical solution. The angular momentum is conserved exactly in the MD method; however, in the DSMC method, the cell sizes must be sufficiently small to conserve approximately the angular momentum because of the statistical assumptions. Both, the twoand threedimensional DSMC-codes have been verified for the hypersonic flow past a circular cylinder and a sphere, respectively. The shock stand-off distance and the pressure distribution along the body surface were compared with experimental results. In both cases, the agreement is very good. As an application to more realistic configurations, the gaskinetic flow past the nose of a typical spacecraft is discussed for different Knudsen numbers.