Characterising drag and wall heat flux reduction of micro-blowing control in compressible turbulent boundary layers

Direct numerical simulations are performed on compressible turbulent boundary layers with micro-blowing controls applied to the walls at a free stream Mach number of 2.0 to investigate the influences of wall-blowing mass flux and spatial arrangements on drag reduction. Using law-of-the-wall for uniform blowing control, an estimation of skin friction is proposed based on Reynolds number and wall-blowing mass flux. At a given Reynolds number, the drag reduction rate increases almost logarithmically with wall-blowing mass flux within the control region. Downstream of the interaction zone, the drag reduction rate increases linearly. The disparities of the drag reduction rate in the integral sense among cases with different spatial arrangements are attributed to the asymmetric pressure gradient associated with flow compression, and expansion at the commencement and termination of the micro-blowing region.