An experimental investigation of the planar turbulent wake in constant pressure gradient

Abstract

This paper describes an experimental investigation into the development of a planar turbulent wake under constant adverse and favorable pressure gradient conditions. The focus of the study is on the near-wake due to its relevance to high-lift systems for commercial transport aircraft. The wake is generated by a flat splitter plate with tapered trailing edge. The pressure gradients are imposed as the wake passes through a wind tunnel diffuser test section with fully adjustable top and bottom wall contours. The streamwise pressure gradients imposed on the wake flow field are held constant in each case. The wake initial conditions are maintained identical upstream of the location where the pressure gradient is first imposed. The use of constant pressure gradients, coupled with identical initial conditions, facilitates isolation of the effect of streamwise pressure gradients on the near-field evolution of the wake and provides a clean test case for computational models. In this paper we focus on characterizing the mean flow widening, streamwise velocity defect variation, and the streamwise evolution of turbulence statistics for both favorable and adverse streamwise pressure gradients. The imposed pressure gradients are shown to have a very significant effect on both the mean and turbulent flow quantities.