URANS COMPUTATIONS OF SHOCK INDUCED OSCILLATIONS OVER 2D RIGID AIRFOIL: INFLUENCE OF TEST SECTION GEOMETRY

摘要

The present article deals with recent numerical results, from on-going research conducted at ONERA/DMAE regarding validation of turbulence models for unsteady transonic flows, for which shock wave / boundary layer interaction develops. The main goal is to predict the onset of Shock Induced Oscillation (SIO) in conditions as close as possible to the experiments. SIO appears over the suction side of a two-dimensional rigid airfoil and leads to the formation of unsteady separated areas. Computations were performed with the ONERA object-oriented software elsA, using the URANS-type approach, closure relationships being achieved by the one-transport equation Spalart-Allmaras model. Applications are provided for the OAT15A airfoil data base built up from tests conducted in the ONERA S3Ch wind tunnel (the airfoil aspect ratio being 3.5). These experiments are well documented for CFD validation with mean, phase-averaged and fluctuating data. Results emphasize the importance of modelling the test section geometry when carrying out 2D unsteady computations to capture SIO as precisely as possible, even though the adaptation of wind tunnel walls had been carefully managed. Lastly, first investigations towards 3D computations (taking into account the four side-walls of the wind tunnel) are presented.