DNS of the interaction between an oblique shock wave and a boundary layer developing along a flat plate Guillaume Fournier 1 , Mohamed Sellam 1 , Amer Chpoun 1 Yann Fraigneau 2 and Christian Tenaud 2 1 Laboratoire de M´ ecanique et d’Energ´ etique d’Evry, Evry, France 2 LIMSI-CNRS, Orsay, France Introduction Interactions between shock waves and boundary layers (SWBLI) are encoun- tered in many industrial applications dealing with supersonic flows (aircraft design, supersonic inlet, rocket nozzles...). If the shock is strong enough, those interactions may cause the boundary layer separation yielding dynamic loads, increased heat fluxes and pressure fluctuations. Even if the physics of SWBLI is not fully understood, it is well known that the separation zone as well as the reflected shock are subjected to a low-frequency streamwise mo- tion that can spread over several tenth of the boundary layer thickness. The origin of this motion is, however, not completely elucidated. Several studies, both numerical 2;11 and experimental 5 , have linked it to the vortex shed- ding in the mixing layer downstream of the separation and a simple model that explains the low-frequency unsteadiness has even been developed 9 . On the other hand, a correlation between the vortical structures in the incom- ing boundary layer and the low-frequency motion have been experimentally found by several authors 1;6 . In addition, recent experiments conducted in the IUSTI supersonic wind tunnel for a deviation angle of 9.5 degrees have shown that the recirculation region is highly three-dimensional 5 . These 3D aspects have been related to two contrarotative vortices developing downstream of the shock. Several nu- merical simulations using LES have been performed for the same geometry, most of them with periodic conditions in the spanwise direction. While the results are in rather good agreement with the experimental data for a weak shock wave, these simulations have failed to capture the three-dimensional aspect of the separation for a 9.5 degrees shock generator angle, demonstrat- ing that the lateral walls of the wind tunnel are, at least partially, respon- sible for the 3D modulations of the recirculating region. The number of 1