Lagrangian aspects of coherent structures in a turbulent boundary layer flow using TR-Tomo PIV and PTV

Abstract

Coherent structures and their role for the fluid exchange mechanisms in the logarithmic layer of a turbulent boundary layer is the focus of the present paper. Extensive experiments have been performed in the water tunnel at TU Delft measuring the particle motion within a volume of a turbulent boundary layer flow along a flat plate at a free stream velocity of 0.53 m/s at Reθ ~ 2460 based on momentum thickness by using time-resolved- tomo PIV and PTV. This data enables a spatio-temporal and topological investigation of the flow structures and related particle motions within a temporally and spatially highly resolved Lagrangian and Eulerian reference frame. Flow statistics of physically relevant quantities from both viewpoints are evaluated in terms of PDF´s, space-timecorrelations, conditional averaging as well as the analysis of single events in order to enhance the understanding of wall bounded turbulence and highlight the potential of this novel technique for turbulence characterisation.