TURBULENT EDDIES IN BOUNDARY LAYERS ON SMOOTH AND ROUGH FLAT PLATE.

This study represents one in a series of boundary layer investigations which are undertaken in order to obtain a definition of the roughness characteristics of a surface from the turbulence structure in the boundary layer near the surface. It is attempted to discuss the effect of the roughness in the structure of the turbulent eddies found near the boundary by comparing space correlations and spectra which were measured in the boundary layer on smooth and rough flat plates. The experimental investigations were made with a flat plate placed at a height of 2. 0 ft. from the floor of a wind tunnel which had a 6 ft. x 6 ft. cross-section. The size of the plate used was 6 ft. x 3 ft. To obtain a rough surface condition, gravel which passed through a no. 7 sieve and are retained on a no. 8 sieve was glued to the surface of the aluminum plate. The density of the roughness material was 120 particles per square inch.