Investigation of 3D Coherent Structures in Turbulent Boundary Layers at High Reynolds Numbers using MultiPulse-STB

Abstract

Large wall shear stress events in turbulent boundary layers (TBLs) produce significant drag and are determined by the dynamics of coherent structures. A fundamental research experiment was performed in the Cross Wind Test Facility Göttingen (SWG) at German Aerospace Center (DLR) in Göttingen, in order to get a deeper understanding in these structures at high Reynolds numbers. For high-resolution studies in the near-wall and logarithmic region, the Multi-Pulse Shake-The-Box (MP-STB) measurement technique for 3D Lagrangian Particle Tracking was applied to a zero pressure gradient flat plate TBL at a Reynolds number of Reθ=10,000. Three dimensional observations of coherent structures even in the near-wall region down to y+=2.5 were done by using quadrant analysis, 2-point correlations and FlowFit visualizations.