MAE Seminar: History Effects in Turbulent Boundary Layers - Spatially and Temporally Varying Pressure Gradients

Abstract: Wall-bounded turbulent flows are ubiquitous in transportation and energy technologies on curving bodies and in unsteady flows. Turbulence is complex even in “canonical” geometries (flat walls, straight pipes and straight channels); geometry curvature and flow acceleration further complicate its study. In this talk, we discuss novel experimental facilities and results toward the systematic characterization of complex pressure gradient and curvature effects, including variable spatial and temporal history. The experiments are carried out using a variable-positioned ceiling and are measured using time-resolved, planar particle image velocimetry. Statistical results are shown for both statically held and dynamic pressure gradients. History effects (prior pressure gradients imposed upstream of the position of interest) and dynamic effects (a dependence on the rate of pressure gradient imposition) are both observed. A hypothesis to explain the observed history effects from a coherent structures perspective is suggested.

Bio: Theresa Saxton-Fox is an assistant professor of aerospace engineering at the University of Illinois at Urbana-Champaign. She received her master's degree and doctorate from Caltech and completed postdoctoral research at Princeton University, prior to starting at the University of Illinois in January 2019. Her work focuses on wall-bounded turbulent flows with particular interests in nonlinear interactions, global unsteadiness and curvature effects. She was awarded the Centennial prize for best thesis in the Department of Mechanical and Civil Engineering at Caltech in 2018 and the Young Investigator Program award from the Office of Naval Research in 2021.