Structure Identification and Analysis in Turbulent Boundary Layers by Stereo PIV

Abstract

Stereoscopic PIV was used to measure three instantaneous components of velocity in streamwise-spanwise planes of a turbulent boundary layer. The local boundary layer thickness was δ = 69 mm, and the corresponding Reynolds number based on friction velocity was 1060. Data sets were obtained in the log region at wall-normal positions of z+ = 92 and z+ = 192. The resulting velocity fields at z+ = 92 revealed distinctive signatures of vortex packets similar to those observed by Adrian, Meinhart, & Tomkins (2000). At this height, trains of 'necks' from hairpin vortices were observed aligned with the streamwise direction. The packets, which were frequently associated with high levels of Reynolds st..