A Numerical Study of Purdue's Mach 6 Tunnel with a Roughness Element

The effects of surface roughness on the stability of hypersonic flow are of great importance to hypersonic vehicles. The overall goal of our research is to provide a better understanding of the effects of surface roughness on transitional and turbulent hypersonic boundary layers. Direct numerical simulations have been performed of flow in the Boeing/AFOSR Mach 6 quiet wind tunnel at Purdue University. Three-dimensional simulations were performed of the nozzle without any roughness and 2D simulations were performed with an isolated roughness element located on the wall of the nozzle. Two different roughness heights were simulated, both of which were less then the local undisturbed boundary layer thickness. The roughness elements produced a combination of Mach wave and expansion fan in the nozzle. The influence of the roughness elements on the flow is investigated in this paper. It is found that the presence of the elements has a substantial effect on the boundary layer and stability profiles downstream of the element.