Accession Number : ADA189285

Title :   The Effects of Longitudinal Roughness Elements Upon the Turbulent Boundary Layer,

Corporate Author : UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES

Personal Author(s) : Blackwelder, R F ; Roon, J B

PDF Url : ADA189285

Report Date : Jan 1988

Pagination or Media Count : 6

Abstract : Velocity profiles and bursting statistics were measured in the presence of cylindrical longitudinal roughness elements (LREs) and compared to similar work by Johansen and Smith. An algorithm was devised to detect low speed streaks (LSS) from the hot-wire rake data, allowing an estimation of the LREs ability to reduce spatial randomeness of the sublayer structure. The velocity profiles agree with Johansen and Smith's result that the effects of the LREs are felt only for y(+) or = 15. The analysis of the bursting statistics and LSS algorithm output shows that the flow relaxes back to a flat plate boundary layer between the LREs. A crude first approximation is that the LREs simply impose the no-slip boundary condition at an elevation equivalent to their diameter. While the LREs might serve as a nucleation site for the LSS, spatial randomness of the structure is effected only very close to the LREs.

Descriptors :   *FLAT PLATE MODELS, *TURBULENT BOUNDARY LAYER, ALGORITHMS, BOUNDARY LAYER, CYLINDRICAL BODIES, ELEVATION, LENGTH, LOW VELOCITY, NUCLEATION, OUTPUT, PROFILES, RAKE ANGLES, ROUGHNESS, SITES, STATISTICS, SUBSURFACE, VELOCITY, HOT WIRE ANEMOMETERS, WIND TUNNELS, BUBBLES, FLOW VISUALIZATION

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE