Organization and Evolution of Coherent Structures in Turbulent Boundary Layers

Ellen K. Longmire

Department of Aerospace Engineering & Mechanics, University of Minnesota, USA

Abstract

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.  

Curriculum Vitae

Ellen Longmire received an A.B. in physics (1982) from Princeton University and M.S. (1985) and Ph.D. (1991) degrees in mechanical engineering from Stanford University .  Prior to receiving her Ph.D., she worked as an engineer at Hauni-Werke Koerber & Co in Germany and at Honeywell and SAIC in the U.S.  Since 1990, she has taught and directed research in the Department of Aerospace Engineering and Mechanics at the University of Minnesota where she holds the rank of Professor.  She uses experimentation and analysis to answer fundamental questions in fluid dynamics that affect industrial, environmental, and biological applications. Recently, her work has focused on single- and multi-phase turbulent flows and liquid/liquid mixtures with surface tension.  She is a Fellow of the American Physical Society and received the UM Distinguished Women Scholars Award (2007), the McKnight Land-Grant Professorship (1994), and the NSF National Young Investigator Award (1994). She currently serves as Editor-in-Chief of Experiments in Fluids.  She previously served as Chair of the American Physical Society Division of Fluid Dynamics (2016), member of the United States National Committee on Theoretical and Applied Mechanics (2011-2015) and Associate Editor of Physics of Fluids (2008-2013).