Direct numerical simulations of supersonic turbulent boundary layer with streamwise-striped wall blowing

Direct numerical simulations of a spatially developing Ma 2.25 supersonic turbulent boundary layer with streamwise-striped wall blowing (SSB) are performed for the purpose of turbulence drag reduction. The SSB is designed to blow through long and straight slots in the flow direction. The slots are equally distributed in spanwise direction, with different stripe spacing and width. Blowing amplitudes of 0.1% and 0.2% are investigated. For comparison, uniform blowing (UB) of 0.1% is also simulated. It is found that in spite of weak control amplitudes, 7.4% and 14.5% drag reduction can be achieved in the case of 6SSB 0.1% and 6SSB 0.2%, respectively. Similar to UB, the boundary layer displacement thickness is thickened by SSB, with a thicker viscous sub-layer and a logarithmic zone which moving away from the wall. Turbulence intensities and turbulent coherent structures are enhanced, although the streamwise scales of the latter are attenuated. Turbulent kinetic energy analysis presents that both the production and dissipation are increased in the near wall. Compressible Renard-Deck decomposition of Cf shows that it is the spatially growth term that mainly responsible for the turbulence drag reduction.