A Parametric Study into the Effects of Surface Roughness Spacing on the Transition of Hypersonic Boundary Layers

Abstract

Preliminary results are presented in this paper for an experimental investigation into the effects of surface roughness on the laminar-turbulent transition of the boundary-layer on a blunted cylinder in a hypersonic flow. Discrete, isolated roughness elements are placed in different configurations on the surface of a blunt nosed cylinder and their effect on the boundary layer assessed at a number of downstream locations. The spacing between the individual elements is investigated and the laminar-turbulent transition characteristics of the boundary layer in the presence of multiple configurations of roughness elements are described. The downstream boundary layer from differently spaced, differently sized pairs of roughness elements are compared to those from a similar, single isolated roughness element and against a smooth reference case to investigate their effects.