A direct-numerical-simulation study of spatially evolving compressible zero-pressure-gradient turbulent boundary layers is presented for a fine-meshed range of Mach numbers from 0.3 to 2.5. The use of an identical set-up for all subsonic and supersonic cases warrants proper comparability and allows a highly reliable quantitative evaluation of compressible mean-flow scaling laws and the settlement on a commonly accepted compressible mean-flow velocity profile in the considered Mach and Reynolds number range. All data are compared to the literature data-base where significant data scattering can be observed. The skin-friction distribution was found in excellent agreement with the prediction by the van Driest-II transformation. Contrary to the prevailing appraisal, the wake region of the mean-velocity profile is observed to scale much better with the momentum-thickness Reynolds number calculated with the far-field-viscosity than with the wall-viscosity. The time-averaged velocity fluctuations, density-scaled according to Morkovin’s hypothesis, are found to be noticeably influenced by compressibility effects in the inner layer as well as in the wake region. Allowing wall-temperature fluctuations affects neither the density nor velocity fluctuations.

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This study extends the input-output framework for the receptivity analysis of an incompressible boundary layer introduced by Ran et al. (Stochastic receptivity analysis of boundary layer flow Phys. Rev. Fluids. 4, 093901, 2019) to the laminar adiabatic supersonic case.Spatially distributed in the wall-normal direction, a delta-correlated Gaussian noise is considered as input, both including the velocity and temperature fields. Similarly, components of the resulting velocity and/or temperature fields are chosen as outputs. To study effects on the boundary layer the measurements of the output are restricted within the δ 99 boundary layer thickness implying, however, that effects like acoustic radiation to the freestream are outside the scope of the present analysis. The main goal of the study is twofold: First, to

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