Piv of a mach 5 turbulent boundary layer over diamond roughness elements
The effects of a periodic diamond roughness (k/= 0.07) pattern on a Mach 4.9 turbulent boundary layer were examined experimentally. Particle image velocimetry and schlieren photography were used to quantify the flow structure over the roughness elements. On average, the roughness elements resulted in increased turbulent fluctuations in the lower half of the boundary layer (compared to a smooth baseline model), and decreased values above y/ ~ 0.5. The turbulent structures within the rough-wall flowfield were stretched along the major axis, while maintaining a nearly constant minor axis (when normalized by ). The structure angles for the rough-wall were increased for y/< ~ 0.3, but then decreased below the smooth wall values for y/> 0.3. It was observed that the rough and smooth Reynolds transverse and shear stresses nearly overlapped, when rotated to their respective local structure angle. This finding suggests that Reynolds stress redistribution is a predominant mechanism that should be included when modeling this class of flow. 2012 by Scott Peltier.