Temporal turbulent flow structure for supersonic rough-wall boundary layers

An experimental study of the temporal turbulent flow structure for high-speed (M = 2.8), high-Reynolds-number (Re/m = 1.9 × 107), rough-wall boundary-layer flow was performed. Six wall topologies consisting of a smooth and five rough surfaces (ks+ = 104-571) were studied. The hot-film measurements consisted of mass-flux power spectra, autocorrelations, cross correlations, integral timescales, and flow structure angle information at three locations (y/δM = 0.25, 0.50, and 0.75) within the boundary layers. The power spectra curves, with inner scaling, were found to shift up and to the right with increasing roughness height at all three boundary-layer locations signifying increased turbulence production and transport. The integral scales decreased with roughness height across the boundary layers, and, for ks+ ≥ 250, were nominally independent of boundary-layer location. The measurements confirmed the inertial subrange indicating that the expected cascade and dissipation mechanisms were present.