Advances in the computation of transonic separated flows over finite wings

Abstract

Transonic flow fields around a low-aspect-ratio wing in a wind tunnel have been simulated using an Euler/Navier-Stokes zonal approach. By using a fast parabolic-type grid generator, a global grid with an H-H topolgy is generated around the wing in which the far-field boundaries match the tests section of the wind tunnel. This global grid, which is a coarse grid, was then subdivided into separate zones. The grid zones near the wing were suitably clustered for viscous resolution, and the Reynolds-averaged Navier-Stokes equations were solved. In the rest of the flow field the Euler equations were solved. Particular emphasis was placed on simulating shock-induced separated flows. Problem areas in the state-of-art computational techniques in wind-tunnel simulations were identified, and each problem was studied in an isolated manner in order to avoid combined effects of multiple sources. The lessons that were learned from those studies were then combined to yield more accurate wind-tunner simulations and to further the understanding of separated flows. As a technology demonstration, one solution with extremely fine grid resolution (1.1 × 10 6 total grid points) was achieved using the Cray-2-superdomputer. Of particular importance for flow physics, a transonic mushroom-type separated flow with counterrotating vortices that closely resembles the experimental pattern, was demonstrated for the first time.