Relaminarization of a turbulent boundary layer with a Mach number $\mathrm{M}_\infty=4$

Results of experimental studies are presented on relaminarization of a supersonic turbulent boundary layer behind an expansion fan for a free-stream Mach number $\mathrm{M}_\infty=4$ within a range of Reynolds numbers $\mathrm{Re}_1 = 8\cdot10^6\div26\cdot10^6$ m$^{-1}$. Experimental data on distributions of the mean velocity and mass-flow fluctuations and the skin friction force are obtained. Partial relaminarization of the boundary layer is reached in the experiments. The calculations of relaminarization criteria show that they can be used to predict the onset of the relaminarization process at high supersonic flow velocities.