USM3D-ME Buffet Simulations of the ONERA OAT15A Airfoil for DPW-8/AePW-4

Numerical simulations of transonic flow over the ONERA OAT15A airfoil using the USM3D-ME solver are carried out in support of the DPW-8/AePW-4 Buffet Working Group Test Case 1a. The aim of this paper is to investigate Reynolds-averaged Navier-Stokes (RANS) model performance for transonic buffet. Two different families of committee-supplied grids developed by Cadence and Helden Aerospace are investigated at a Mach Number (M∞) of 0.73 and a chord Reynolds Number of 3.0x106. Results indicate that the two families of grids provide different solutions based on their respective mesh generation philosophy. Although grid convergence is achieved for Cadence grids, no oscillatory behavior associated with buffet is observed. In comparison, grid convergence is not achieved for the HeldenMesh grids due to the presence of oscillations in the flow field. The HeldenMesh grid solutions also predict the shock content in an improved manner due to the increased mesh density around the shock location. Based on the results, it is demonstrated that RANS models are able to capture the pre-buffet conditions and the onset of buffet with some accuracy, however temporal accuracy is a necessity for the prediction of accurate physics associated with buffet.