Investigation of the Law-of-the-Wall for a Turbulent Boundary Layer Flow Subject to an Adverse Pressure Gradient Using Particle Imaging

We present an experimental investigation and data analysis of a turbulent boundary layer flow at a significant adverse pressure gradient for two Reynolds numbers \(Re_\theta =6200\) and \(Re_\theta =8000\). We perform detailed multi-resolution measurements by combining large-scale and long-range microscopic particle imaging. The flow is designed to be close to equilibrium in the sense that characteristic integral flow parameters evolve slowly in streamwise direction to study scaling laws for the mean velocity and for the total shear stress in the inner part of the boundary layer. In the inner part of the inner layer the mean velocity can be fitted by a log-law. We observe larger values for the log-law slope than in zero-pressure gradient flows and study possible history effects. The outer part can be described by a modified log-law, which depends on the pressure gradient parameter and on a parameter for the effect of the mean inertial terms. Finally we present a new composite profile for the mean velocity.