Practical Navier-Stokes computation of axisymmetric reentry flowfields with coupled ablation and shape change

Abstract

An implicit numericalmethodfor the fullhiavierStokes equations is merged with material-response technology for carbonaceous materials to yield two-dimensional transient solutions where the flowfield and material response are closely coupled. The vehicle surface temperature and the heat shield ablative rate are computed as the resultants of an energy balance at the solid-gas interface, including the transient effects of in-depth heat conduction. The diffusion of ablation products is computed with a two-species, lumped-parameter model. The recession of the surface and change of shape of the vehicle are computed dynamically in real time. A test computation is performed for a typical ballistic reentry vehicle, covering the altitude band from 43 km to sea level. v b d u c t ion Current methods used to predict the aerodynamics and heating of reentry vehicles concentrate attention on some aspects of the problem at the expense of others, partly due to historical reasons in the development of these methods, and partly to limitations of the computing equipment. Thus, aerodynamic methods concentrate on the flowfield, and rely on other methods to provide material-response characteristics such as surface temperature and ablation rates. On the other hand, material-response methods concentrate on the physical and chemical processes associated with surface ablation and heat conduction in the interior of the nosetip or heat shield in order to predict surface temperature, ablation rates, and internal temperatures, using correlations or highly simplified approaches to provide the aerodynamic loading and heating acting on the surface of the vehicle. However, in reality all these phenomena are highly coupled. For example, the aerodynamic heat flux to the vehicle deDends to the first order on its surface * **