Computations of flow field over Apollo and OREX reentry modules at high speed

Abstract

The paper describes a numerical simulation of the viscous flow past the Apollo and the OREX (Orbital Reentry EXperiments) configurations for freestream Mach numbers range of 1.2-5.0. The flow fields over the reentry module are obtained by solving time-dependent, axisymmetric, compressible Navier-Stokes equations. The fluid mechanics equations are discretized in spatial coordinate employing a finite volume method, which reduces the governing equations to semi-discretized ordinary differential equations. Temporal integration is carried out using a two-stage Runge-Kutta time-stepping scheme. A local time-stepping is used to obtain the steady state solution. The numerical simulation is done on a single-blocked structured grid. The flow field features around the reentry capsules such as bow shock wave, sonic line, expansion fan and recirculating flow in the base-shell region are well captured by the present numerical computation. A low pressure is observed immediately downstream of the base which is characterized by a low-speed recirculating flow region, which can be attributed to fill-up in the growing space between the shock wave and the reentry module. The effects of the module geometrical parameters, such as radius of the spherical cap radius, shoulder radius, cone angle and back shell inclination angle on the flow field, which will provide a useful input for the optimization of the reentry module.