Near-wall flow features in ZPG-TBL at various Reynolds numbers using dense 3D Lagrangian Particle Tracking

Abstract

The 3D Lagrangian particle tracking method Shake-The-Box (STB) and, subsequently, the data assimilation method FlowFit have been applied to measure the flow field in a narrow wall-parallel volume inside the near-wall region of a zero-pressure-gradient (ZPG) turbulent boundary layer (TBL) flow at various Reynolds numbers. The STB experiments have been conducted in the 1m- wind tunnel facility of DLR in Göttingen. The results show that the chosen methodology is able to resolve almost all features of the flow inside the viscous sub-, buffer- and lower logarithmic- layer in space and time. The gained data consists of time-series of spatially well resolved 3D velocity, acceleration and pressure fields, as well as a huge amount of long Lagrangian particle trajectories. Selecting the viscous sublayer part of the measurement volume provides time-series of the 2D distribution of both components of the instantaneous wall-shear stresses (spatially coarser resolved at the higher Reynolds numbers). The resulting data are suited for conditional and time-resolved 3D analyses of coherent structures, rare (e.g. back flow) events and various one- and multi-point statistics.