Direct Numerical Simulation of High-Speed Turbulent Flows over Complex Rough Surfaces

We perform direct numerical simulations of supersonic and hypersonic turbulent flows over complex rough walls in open channel configurations, targeting bulk Mach numbers up to Mb = 6. The surface topography is generated using a spectral synthesis technique that allows us to generate realistic Gaussian roughness.

The study aims to evaluate how geometric complexity interacts with compressibility in shaping mean profiles, turbulent structures, wall friction, and heat flux. A compressibility-sensitive roughness Reynolds number is being developed to account for local viscosity and density variations near the roughness crests, enabling consistent comparisons across flow regimes. The validity of classical compressibility transformations is also assessed throughout the simulation campaign. This work contributes to a deeper understanding of how roughness geometry influences high-speed wall-bounded flows and lays the foundation for improved modelling strategies in realistic hypersonic boundary layers.