Abstract: To examine the statistical characteristics of skin friction of shock wave/turbulent boundary layer interaction, the direct numerical simulation method was used to obtain the exact flow field of the shock wave/turbulent boundary layer in a hollow cylinder-flare configuration at Mach 6. The decomposition formula of averaged skin friction was derived and studied together with the convection item, streamwise inhomogeneity item, molecular viscous item, curvature effect item, and turbulent kinetic energy dissipation item. The statistical characteristics of fluctuating skin friction and averaged skin friction were explored. Probability density functionresults indicate that the fluctuating skin friction deviates from the normal distribution in the interaction region with distinct intermittency. Power Spectrum Density results show that energy of skin friction plays the main role in middle frequency zone whose peal location is 0.14 before interaction while it does in higher frequency zone after interaction. After the decomposition of the averaged skin friction, the molecular viscous item and turbulent kinetic energy dissipation item mainly contribute to the averaged skin friction. Before the interaction region, the molecular viscous item plays the main role, while after the interaction region, the turbulent kinetic energy dissipation item dominates. After the interaction, the convection item becomes stronger than before the interaction, the curvature effect item remains the same, and the streamwise inhomogeneity item turns negative from positive before the interaction, which is caused by the change in the pressure gradient item. Moreover, the fact that different regions in the boundary layer indicate different flow features leads to different contributions to the averaged skin friction, particularly for the turbulent kinetic energy dissipation item.

Key words: shock wave/boundary layer interaction, direct numerical simulation, unsteady flow, decomposition of skin friction, statistical analysis