Wake Behavior in the Presence of Free Stream Turbulence

Abstract

The effect of free stream turbulence on the characteristics of a turbulent wake developed from the trailing edge of a thin and smooth flat plate was studied analytically and experimentally. The experimental measurements were taken in a low speed wind tunnel using cross-wire anemometry. Two levels of free stream turbulence were obtained at the leading edge of the flat plate using grids with square bars (T∼5.23 percent) and circular rods (T∼7.23 percent). The grids were kept at distance of 273 mm from the leading edge of the flat plate. Experimental results are presented on the mean velocity profile, wake center-line velocity, half wake width, displacement thickness, and shape factor. It is shown that the free stream turbulence increases the wake recovery and growth rates. The semi-empirical correlations are developed to predict the foregoing behavior. The analytical investigation also lead to the establishment of the two turbulence parameters. These parameters simulate the effect of free stream turbulence on the wake velocity (U0 ) and length (L0 ) scales.