GALCIT Colloquium

Because of their practical importance in determining drag on transport vehicles, turbulent boundary layers have been the subject of intense study for many decades.  The complexity of these flows makes it challenging to advance our understanding of the fundamental physics and how it varies over a range of Reynolds numbers.  This talk will focus on our experience using planar and volumetric velocimetry techniques to investigate the nature of turbulent boundary layers with moderate Reynolds number.  The velocity fields obtained are analyzed to quantify and understand the structure and organization of coherent eddies as well as their relation to regions of long streamwise coherence in the logarithmic region.  In the logarithmic region, extended packets of eddies, which can be tracked over significant distances, contribute a significant fraction of the Reynolds stress and are therefore important contributors to drag.  Our efforts to manipulate the packet organization and to understand packet recovery from perturbations will be discussed.