An Experimental Investigation Of The Effects Of Several Types Of Surface Roughness On Turbulent Boundary Layer Characteristics At Supersonic Speeds

A theory is described which can be used to predict accurately the skin friction drag of surfaces with uniform grain-type roughness. The roughness does not necessarily have to extend to the leading edge of the surface for an accurate calculation to be made. Uniform surface roughness composed of spherical beads does not affect the boundary layer in a manner significantly different from grain-type roughness, provided that the grains and the spheres are bonded to the surface in a similar manner. Consequently, the theory accurately predicts the effects of spherical roughness elements on skin friction under these conditions. The effect of a given type of roughness on turbulent boundary layer characteristics is strongly dependent upon the density of distribution of the roughness elements. The effect of maximum density V-grooves on turbulent boundary layer characteristics is dependent upon the sweepback angle. The effect of increasing sweepback is to reduce the skin friction drag. (Author).