APPROACH OF TURBULENT BOUNDARY LAYER TO SIMILARITY.
COLORADO STATE UNIV FORT COLLINS FLUID MECHANICS PROGRAM
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A large scale turbulent boundary layer with no pressure gradient, developed on a flat plate 95 feet long was investigated. Theoretical considerations of the existence of local similarity yield the requirements which should be found in the turbulent boundary layers in order that similarity exists. Measurements of the mean motion, the turbulent velocity components and the turbulent shear stress were made for the free stream velocity range 60 to 100 ftsec. Reynolds numbers based on the boundary layer thickness were of the order of 1,000,000. Turbulence quantities were evaluated from a single rotating hot-wire probe along the entire length of the boundary layer. For all quantities measured, the uncertainty intervals were calculated in order to provide a measure of the reliability of the results. The large scale turbulent boundary layers are shown to approach closely the theoretical requirements for similarity. Displacement and momentum thickness grow as a linear function of x-coordinate, the form factor is constant. The constant wall shear stress requirement is very closely approached. An asymptotic similarity form is considered and reported. For similarity function of the turbulent shear stress distribution across the boundary layer thickness, an approximate linear function is proposed. The best average universal velocity profile is tabulated. Author
- Fluid Mechanics