Numerical investigation of the effect of wall cooling on hypersonic turbulent boundary layers*

The interest in transitional and turbulent compressible boundary layers has been revitalized in recent years due to an increasing interest in minimizing the frictional drag of hypersonic vehicles. At low and moderate supersonic freestream Mach numbers, experimental and numerical results revealed that the validity of Morkovin's hypothesis (referring to the resemblance between incompressible and compressible wall turbulence structures) cannot be disputed. However, as the Mach number is increased towards high supersonic and hypersonic regimes, turbulent flow structures are modified and enhanced by intense fluctuations of density and pressure, which can be even more pronounced if the wall temperature varies adiabatically. In this work, we study the effect of wall cooling on a hypersonic turbulent boundary layer by direct and large eddy simulations, via a simple and robust re-scaling and recycling method. We considered both constant and localized wall cooling in our analysis and monitor both statistical and structural characteristics of turbulence evolving at the wall.