Lagrangian and Eulerian aspects of a turbulent boundary layer flow - An investigation using time-resolved tomographic PIV

Abstract

The momentum exchange mechanisms in a turbulent boundary layer (TBL) flow are of manifold temporal and spatial scales and governed by the organization of self-sustaining coherent flow structures driven by entrained high momentum fluid. Generic flow structures such as hairpin-like vortices and spanwise alternating wall bounded low- and high-speed streaks have been observed and extensively analyzed with both experimental and numerical methods, e.g. by means of PIV or DNS. In many studies the role of these structures for the wall normal and spanwise fluid exchange has been highlighted mostly within an Eulerian reference frame. But for a full understanding of the momentum exchange in turbulent wall flows a step towards a spatially resolved Lagrangian frame of reference would be advantageous. The data achieved from the present application of time-resolved tomographic PIV to a flat plate turbulent boundary layer flow in a water tunnel at Re ~ 2460 enables for the first time a topological investigation of the flow structures and related particle motions within a temporally and spatially resolved Lagrangian and Eulerian reference frame.