DNS of shock boundary layer interaction: study of the shedding intermittency.
Abstract
Under certain circumstances (High Mach number, large shock angle...), the interaction between
an incident shock wave impinging a boundary layer may create an unsteady separation bubble.
This bubble, as well as the subsequent reflected shock, are known to oscillate in a low-frequency
streamwise motion that can spread over several tenth of the boundary layer thickness. The
origin of those oscillations, however still unclear, has been related either to the shedding of
vortices in the mixing layer downstream of the separation, or to the turbulent structures in
the incoming boundary layer. An in-house parallel (MPI) Finite-Volume based DNS/LES
solver developed at LIMSI-CNRS is used to perform simulations of this problem. In order
to reduce the possible causes of unsteadiness to the sole vortex shedding, simulations have
been performed for laminar boundary layers, in which no incoming structures are encountered
within the boundary layer. In this configuration, low frequency oscillations of the whole shock
wave boundary layer interaction system (SWBLI) have not been observed even if a strong
intermittency of the shedding responsible for low-frequency reattachment shock oscillations have
been evidenced. This tends to suggest the importance of the turbulent structures of the incoming
boundary layer in the low frequency oscillations of the SWBLI system. In this context, the
accurate simulation of a turbulent compressible incoming boudary layer is of great importance.
A Synthetic Eddy Method [3], adapted to compressible flow, have been employed to achieve
this objective without prohibitive additional computational costs. Analyses of the SWTBLI
dynamics by using a modal decomposition will be presented at the conference.