Mach Number and Wall Temperature Effects on Turbulent Boundary Layers

We present a direct numerical simulation database of supersonic and hypersonic turbulent boundary layers. The parametric studies include varying freestream Mach number in the range of 3 to 8 and wall-temperature condition for wall-to-freestream ratio of 2 to 5.5. We find that there is no significant effect of the Mach number on the turbulence production mechanisms and overall dynamics. Rather, the Mach number effects are local, affecting the extent of the turbulence structures. The wall cooling is a sink of energy. Thus, the near-wall region is more quiescent for colder boundary layers. For data with different wall temperature, a better collapse is found using a coordinate transformation that takes into account the variation in density and temperature across the boundary layer. Evidence of hairpin packets in the compressible DNS data is shown