Turbulent Boundary Layers Developing over Equispaced Circular Wires Parallel to the Trailing Edge of a Flat Plate

摘要

Turbulent boundary layers subjected to a sudden change in boundary condition from a smooth flat-plate to a “rod wall” with two-dimensional openings have been studied experimentally. The rod wall consists of circular wires, which are equally spaced in the streamwise direction and whose diameter is the same as the thickness of the upstream plate. Three different spacings of wires are tested; the spacings are two to four times of wire diameter. Comparative measurements are made on rough walls which are geometrically the same as the rod walls but have no openings. With decreasing the wire spacing, the internal layer formed downstream of the change in wall condition develops faster and the turbulence intensity of longitudinal velocity component becomes larger. Pronounced maximum occurs in the transverse distribution of the flatness factor of velocity fluctua- tion, which yields a measure of the internal-layer thickness.