Flow properties of compressible and incompressible subsonic turbulent boundary layers with surface roughness
An experimental study of the effects of surface roughness on subsonic turbulent boundary layer flow (Re/m = 2.5 106), both incompressible (M = 0.22) and compressible (M = 0.65), was conducted. The study consisted of the testing of six different rough wall surfaces (k+ = 705 - 1405), including a smooth plate, three random sand-grain plates, and two uniformly spaced machined plates. The mean flow data that was recorded included velocity, temperature, and density measurements using pitot-probe and hot-film anemometry. Measurements of the skin friction coefficients for each plate were taken using a variety of different analytical and experimental techniques, including integral methods, velocity methods, and the use of direct measurement skin friction gages. Turbulence intensity data and Reynolds shear stress data using hot-film anemometry was collected for the incompressible case. The turbulence data is presented with inner, outer, and mixed variable scaling. The velocity profiles and velocity defect follow the expected trends according to the roughness height. It was also found that, unlike the supersonic case, the turbulence information demonstrated a roughness dependency.