Investigation of a high Reynolds number turbulent boundary layer flow with adverse pressure gradients using PIV and 2D- and 3D- Shake-The-Box

Abstract

We present an experimental adverse pressure gradient turbulent boundary layer (TBL) flow investigation at high Reynolds numbers (approx. 10.000 < Re < 40.000) using large field Multi camera 2D PIV and three different particle tracking methods based on the Shake The Box (STB) technique, namely time resolved 2D and 3D STB and Multi Pulse (MP) STB. The experiments were performed within the frame of the DLR project Victoria and conducted in the Eiffel type atmospheric wind tunnel of the University of Armed Forces in Munich (AWM), which has a 22m long test section with a rectangular cross section of 1.8 x1.8 m^2. After a ramp the TBL develops along a flat plate with nearly zero pressure gradients (ZPG) to an equilibrium state before it enters into a 2D diffusor geometry following a smooth and moderate curvature into a flat plate at ~18° inclination angle while undergoing a significant adverse pressure gradient (APG) leading to flow separation. The measurements have been performed with an embedded field of view (FOV) strategy. A statistical significant number of samples for four different free stream velocities have been acquired at several positions in all pressure gradient regimes down to the region of (intermittent) flow separation. A large number of instantaneous velocity vector fields and time resolved particle tracks of the boundary layer flow have been achieved in order to gain high resolution wall normal profiles of the mean velocities and related Reynolds stresses <u_i u_j> in a first step.