Planar shock-wave boundary-layer interaction

Semi-confined Flows

Underlying Flow Regime 3-32

Abstract

The interaction between a shock wave and a boundary layer remains an issue for both applications and basic research. In aeronautical situations, such interactions are at the origin of unsteadiness which may be detrimental for air frames and mechanical structures. The understanding of such phenomena is not always clear because the frequencies involved in the unsteadiness are much below any other characteristic frequency in the flow (see Dolling 2001 and Smits and Dussauge 2006 for reviews). Only a few interpretations have been proposed, although recent attempts seem to offer more comprehensive views (see Dupont, Debiève, Dussauge 2011 for example). A severe test case is proposed in the European program UFAST (Unsteady eFfects of shock wAve induced SeparaTion) to illustrate this problem: the reflection of an oblique shock on the turbulent boundary layer of a flat plate at a Mach number of 2.25, at different angles of deviation producing different cases of separation. This well documented experiment is presented, including mean and turbulent flow measurements together with spectral measurements to determine the dominant frequencies of the unsteadiness. Of course RANS model can only provide a global description of mean quantities. More advanced models like LES or DES have the ability to capture the unsteadiness. Comparisons with LES and DES numerical simulations are presented and discussed, and best practice guidelines are proposed. These studies are available in the UFAST database, as published in Doerffer 2009 and in Doerffer et al. 2010.