EFFECTS OF ELEVATED FREE-STREAM TURBULENCE ON FLOW AND THERMAL STRUCTURES IN TRANSITIONAL BOUNDARY-LAYERS

The effects of elevated free-stream turbulence on flow and thermal str uctures in transitional boundary layers were investigated experimental ly on a heated flat plate. Detailed boundary layer measurements using a three-wire probe and wall heat transfer were made with free-stream t urbulence intensities of 0.5, 3.8, 5.5, and 6.4 percent, respectively. The onset of transition, transition length, and the turbulent spot fo rmation rate were determined. The statistical results of the streamwis e and cross-stream velocity fluctuations, temperature fluctuation, Rey nolds stresses, and Reynolds heat fluxes were presented. The eddy visc osity, turbulent thermal diffusivity, and the turbulent Prandtl number were calculated and related physical mechanisms are discussed.