Shock-boundary layer interaction (SBLI) is frequently met in supersonic engine inlet flow and external flow. A detailed study on the mechanism of reduction of shock induced flow separation by micro-vortex generator (MVG) is carried out by high order implicit large eddy simulation (ILES). To generate the fully developed turbulent inflow, a series (20,000) of turbulent profiles are given by our previous DNS results. The mechanism of reduction of shock induced flow separation by MVG was originally considered as a result of streamwise vortex mixing. It was thought that the mixing would result in a plump turbulent velocity profile which has stronger separation resistance. It was claimed that turbulent flow has so strong mixing that the velocity profile becomes plump, which lead to reduction of shock induced flow separation. However, according to our LES study reported in this paper, the real mechanism of flow separation reduction is that the shock wave breaks down and disappears when the ring-like vortices generated by MVG are passing through the shock. On the other hand, the vortex structures never break down and is influenced very little when they pass the shock wave. Therefore, the shock induced flow separation is reduced by moving ring-like vortices which were generated by MVG through the manner to break down the shock wave, but mainly not by the streamwise vortex mixing which produces a plump velocity profile in the boundary layer. Details of the investigation on the mechanism are reported in this paper.
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