Approximate Two Layer (Inviscid/Viscous) Methods to Model Aerothermodynamic Environments

Abstract

Approximate inviscid and boundary layer techniques for aerodynamic heating calculations are discussed. An inviscid flowfield solution is needed to provide surface press ures and boundary-layer edge properties. Modified Newtonian pressures coupled with an approximate shock shape will suffice for relatively simple shapes like sphere-cones with cone half-angles between 15 deg and 45 deg. More accurate approximate methods have been developed which make use of modified Maslen techniques. Slender and large angle sphere-cones and more complex shapes generally require an Euler code, like HALLS, to provide that information. The boundary-layer solution is reduced significantly by using the axisymmetric analog and approximate heating relations developed by Zoby, et al. Analysis is presented for the calculation of inviscid surface streamlines and metrics. Entropy-layer swallowing effects require coupling the inviscid and bouodary-layer solutions.

Calculated heating rates were found to compare well with experimental data and a thin-layer Navier-Stokes Code LAURA for sphere-cones and shuttle configurations. When surface pressures are prescribed or assumed, instead of using an Euler code, heating rates are calculated reasonably well for those cases where the surface pressures are accurate.