Effects of Elevated Free-Stream Turbulence on Flow and Thermal Structures in Transitional Boundary Layers

Abstract

The effects of elevated free-stream turbulence on flow and thermal structures in transitional boundary layers were investigated experimentally on a heated flat plate. Detailed boundary layer measurements using a three-wire probe and wall heat transfer were made with free-stream turbulence intensities of 0.5, 3.8, 5.5, and 6.4 percent, respectively. The onset of transition, transition length, and the turbulent spot formation rate were determined. The statistical results of the streamwise and cross-stream velocity fluctuations, temperature fluctuation, Reynolds stresses, and Reynolds heat fluxes were presented. The eddy viscosity, turbulent thermal diffusivity, and the turbulent Prandtl number were calculated and related physical mechanisms are discussed.