3D LAGRANGIAN PARTICLE TRACKING AND DATA ASSIMILATION IN WALL-BOUNDED TURBULENCE

Abstract

Wall-bounded turbulent flows at technically relevant Reynolds numbers still attract high attention in fluid mechanics due to the wide range of spatial and temporal scales involved in the transport of turbulent kinetic energy from the outer flow towards the wall and its back scatter. Especially, the measurement of high velocity gradients in the near-wall flow field e.g. the instantaneous friction velocity field and the role of coherent flow structures for the interaction of the flow with the wall is not fully understood. With the 3D Lagrangian particle tracking method Shake-The-Box (STB) and, subsequently, the data assimilation method FlowFit one can gain time-series of spatially resolved 3D velocity, acceleration and pressure fields including Lagrangian trajectories and both components of the instantaneous wall-shear stresses suited for (conditional) analysis of coherent structures, rare (e.g. back flow) events and oneand multi-point statistics.