Dept. of Mechanical Engineering Graduate Seminar

PRESENTATION: Our work is motivated by the need to understand and predict turbulent particle-laden flows across a range of environmental and industrial applications. In this talk, we consider a relatively canonical yet challenging experimental flow designed to be accessible to direct numerical simulation. A spherical particle in a turbulent boundary layer undergoes complicated particle-wall and particle-turbulence interactions. Particles with significant diameter are subject to variations in shear and normal forces around their circumference. Wall friction will affect the particle rolling and sliding motions while coherent flow structures can lift the particle away from the wall. To resolve the sphere dynamics in such a flow, 3D tracking experiments were conducted in a water channel facility. The translation and rotation of individual spheres released from rest were tracked over distances of 6d for multiple flow Reynolds numbers and particle-to-fluid density ratios. Simultaneous stereoscopic PIV measurements were acquired in the logarithmic region surrounding the moving spheres. While neutrally buoyant particles typically lift off from the wall upon release, denser particles travel mostly along the wall. The relative contributions of turbulence, wall friction, and mean shear to the resulting particle motions will be discussed for the different cases considered.

PRESENTER: Ellen Longmire is a Professor of Aerospace Engineering & Mechanics at the University of Minnesota. She received an A.B. in physics from Princeton University and M.S. and Ph.D. degrees in mechanical engineering from Stanford University. 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 a member of the US National Committee on Theoretical and Applied Mechanics. She previously served as Associate Dean of Academic Affairs for Science & Engineering at University of Minnesota, Chair of the APS Division of Fluid Dynamics, and Associate Editor for Physics of Fluids.