A Comparison of Different Approaches for Predicting Transonic Buffet Onset on Infinite Swept Wings

Abstract

A comparative study is performed on three different approaches for prediction of transonic buffet onset on infinite swept wings. All three approaches are based on the unsteady Reynoldsaveraged Navier–Stokes (URANS) equations, and include: quasi-3D and fully-3D global stability analysis of the corresponding steady 2.5D RANS solutions and direct numerical solution of the 3D URANS equations. The results are presented for an infinite swept wing based on the ONERA OAT15A airfoil section. The quasi-3D stability analysis is shown to be accurate and most efficient and, thus, is best suited for this spanwise-uniform flow. The fully-3D stability analysis ensures the same accuracy, provided that the grid-step in the spanwise direction is sufficiently small. It is much more demanding in terms of computer memory but can be extended to more-general wing configurations. Good agreement is observed between the three approaches in terms of critical conditions for buffet onset and the instability growth characteristics, providing a cross-validation of the methods and an assessment of their computational demands