An experimental investigation of symmetric and asymmetric turbulent wake development in pressure gradient

Abstract

This paper examines and contrasts the response of planar turbulent wakes with initially symmetric and asymmetric mean velocity profiles to identical imposed streamwise pressure gradients. The focus on near wake behavior, profile asymmetry, and pressure gradient is motivated by their relevance to high-lift systems for commercial transport aircraft. In the experiments, the symmetric wake is generated by a flat plate with a tapered trailing edge. Active and passive flow control are applied on an identical second plate in order to generate the asymmetric wake. Both favorable and adverse constant pressure gradients are imposed on the wakes by means of a downstream diffuser section with fully adjustable top and bottom wall contour. For both symmetric and asymmetric wakes, the effect of pressure gradient on wake spreading, mean velocity defect decay, and the streamwise evolution of the turbulent stresses are documented in detail. In this manner, the role of asymmetry in strained wake development is isolated. We also gauge the ability of commonly used one- and two-equation turbulence models to predict the streamwise wake evolution observed in the experiments.