Techniques for compressible flow calculations on multi-zone grids

Abstract

In order to simulate inviscid/viscous compressible flowfields about 3-D realistic aerodynamic bodies, the combined use of an implicit, upwind biased real gas scheme with 3-D fully conservative patched grid techniques is discussed. An "equivalent" gamma formulation is implemented in order to model real gas effects in Van Leer's flux vector splitting (FVS) and Roe’s flux difference splitting (FDS) scheme. A hybrid approximate-factorization (AF)/relaxation algorithm is used as an efficient solver of the Euler, parabolized Navier-Stokes, and thin-layer Navier-Stokes equations. Two different approaches, clipping and Ramshaw’s rezoning algorithms, for performing a conservative flux calculation are described and compared in terms of numerical efficiency. In order to show the real gas \\\ effects in the upwind schemes, two tcst problems are solved. Also to demonstrate the capability of the patched grid approach, the turbulent flowüeld about 3-D analytic forebody is calculated as another test problem. Due to the poor results of the Baldwin-Lomax turbulent model for separated flows, only the attached flowtield is considered in the analytic forebody calculation. Finally, as applications of this approach, the inviscid/viscous flowfields about several aerodynamic bodies are calculated including a generic hypersonic aircraft, a model of the SR-71 aircraft, and F-18 forebody with strakes.