Turbulence In A Hypersonic Compression Ramp Flow

A hypersonic shock wave/turbulent boundary layer interaction (STBLI) is investigated using direct numerical simulation (DNS). The geometry is an 8 degrees compression ramp, and the flow conditions upstream of the interaction are Mach 7.2 and Re-theta = 3500. Consistent with experiments at similar conditions, the flow is found to be attached in the mean, although the DNS shows that the probability of observing reversed flow on an instantaneous basis is significant. Due to the high Mach number of the flow combined with a low deflection angle, the shock angle is shallow and the shock is immersed in the boundary layer for a streamwise distance equal to several incoming boundary layer thicknesses downstream of the compression corner. The instantaneous flow structure observed in the DNS is in good qualitative agreement with filtered Rayleigh scattering images obtained experimentally that are available in the literature. The behavior of the turbulence is described based on the evolution of the Reynolds stresses, the anisotropy tensor, the wall pressure spectra, and the turbulence kinetic energy budget through the interaction. The various Reynolds stress components are found to be amplified by factors of 1.8-2.5. The heat transfer through the interaction is also investigated, as well as the relationship between the velocity and temperature fields. At the corner and for a significant distance downstream of the corner, the Reynolds analogy factor lies above values typically observed in zero-pressure-gradient hypersonic boundary layers. A common heat-transfer-pressure scaling describes the behavior observed in the DNS more accurately but with some departures near the corner. In the present attached STBLI, the strong Reynolds analogy, including the assumption of a constant turbulent Prandtl number around unity, is satisfied reasonably well in the interaction, although there are significant departures in the near-wall region.