Effects of Free Stream Turbulence on Turbulent Boundary Layer on a Flat Plate with Zero Pressure Gradient : 3rd Report, Contribution of Turbulent Length Scales

Abstract

The effects of free stream turbulence on the Reynolds stress and the turbulent heat flux in the turbulent boundary layer on a flat plate are studied experimentally. The measured turbulent quantities in the turbulent boundary layer are classified into four quadrants. From these measurements, the following results are obtained. As to the temperature field, the contributions of the sweep-type motion are greater than those of the ejection-type motion for the near-wall region with increasing free stream turbulence, and as to the flow field, the contributions of both types of motions are larger than they are in the case of no turbulence grid. The measured enhancement rates of the heat transfer coefficient and the wall friction coefficient are determined from the intensity of free stream turbulence and from the integrated turbulent length scales in the free stream.