Effect of Surface Roughness on Hypersonic Turbulent Boundary Layers

Direct numerical simulation (DNS) of a Mach 4.9 turbulent boundary layer negotiating periodic crosshatch (i.e., diamond) roughness is performed to generate physical understanding of hypersonic, rough-wall boundary layers. The freestream conditions and roughness geometries of the DNS match those tested at Texas A&M University (TAMU) and direct comparison with the TAMU experiments is first conducted. Boundary-layer statistics from the DNS are then presented to provide detailed insights into the scaling of turbulence characteristics and their dependence on roughness parameters. Data-driven techniques including dynamic mode decomposition (DMD) and spectral proper orthogonal decomposition (SPOD) are also performed to understand the effect of roughness on coherent structures and their impact on surface thermo-mechanical loading.