Vortex distribution and interaction within a perturbed turbulent boundary layer
University of Minnesota Twin Cities
Abstract
Discrete objects immersed in a turbulent boundary layer disturb the existing turbulent eddies and their organization. In environmental flows, the characteristics, evolution, and downstream persistence of the disturbance can affect sediment and nutrient transport as well as the underlying shear stress on a seafloor or riverbed. In the current work, we consider flow downstream of a cylinder in crossflow mounted parallel to and above the bounding surface. Key parameters of interest include D/δ and G/δ, where D represents the cylinder diameter, G is the gap between the cylinder bottom and the wall, and δ is the boundary layer thickness. The goal is to understand the effects of flow downstream of relatively small cylinders (D/δ ~ 0.1) embedded in the logarithmic region, where unperturbed turbulence levels are high and the oncoming flow includes coherent structures spanning a range of length scales. Both D/δ and G/δ are varied to investigate wake-induced perturbations and how they interact with the typical eddies and structures in the unperturbed flow. The results of planar PIV measurements obtained in cylinder wakes embedded in a boundary layer with Reτ = 1300 will be discussed in terms of instantaneous and averaged quantities. In addition, a resolvent-based phase estimator will be discussed and then applied to interpret spectral content in the otherwise uncorrelated data fields.
About the speaker
Dr. Ellen Longmire received an A.B. in physics from Princeton University and M.S. and Ph.D. degrees in mechanical engineering from Stanford University. She has taught and directed research in the Department of Aerospace Engineering and Mechanics at the University of Minnesota since 1990 and recently served as Associate Dean of the College of Science and Engineering. Professor Longmire uses experimentation and analysis to answer fundamental questions in fluid dynamics that affect aerospace, industrial, biomedical, and environmental applications. She is a Fellow of the American Physical Society and received the UM Distinguished Women Scholars Award, the McKnight Land-Grant Professorship, and the NSF National Young Investigator Award. She is currently an Editor-in-Chief for Experiments in Fluids and ex officio member of the US National Committee on Theoretical and Applied Mechanics. She previously served as Chair of the APS Division of Fluid Dynamics and Associate Editor for Physics of Fluids.
