We investigate rarefaction effects in compressible turbulent boundary layers by conducting direct numerical simulations by imposing slip boundary conditions at the wall. Such a simulation method is justified by the observation that the Kolmogorov and viscous length scales are an order of magnitude higher than the molecular mean free path. The influences of the slip boundary conditions on turbulent flow statistics are restricted within the viscous sublayer. Despite their minor impacts on the mean velocity and skin friction, the mean wall heat flux, vorticity, and velocity divergence fluctuation intensities are obviously affected.

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• Compressible boundary layers
• High-speed flow
• Rarefied flows
• Turbulence