Mechanical Engineering Stewart Harris Seminar Series

Ebenezer P. Gnanamanickam, Ph.D

Professor of Aerospace Engineering
Embry-Riddle Aeronautical University

Abstract:

Flexible hair-like roughness elements serve as mechanosensory receptors in many arthropods and aquatic species, including the lateral line sensors of fish and airflow sensors of bats. These receptors often operate in turbulent environments, where their interaction with the surrounding flow is inherently nonlinear. This work examines the coupled dynamics between wall-bounded turbulence and arrays of such sensors, abstracted as flexible micropillars. Experiments were conducted in a turbulent boundary layer over micropillar arrays with systematically varied geometric and mechanical properties, ranging from small patches on the order of the boundary layer thickness to extended fetches spanning several boundary layer thicknesses. For most configurations, the micropillars resonated in response to the background turbulence and, in turn, modified the near-wall turbulence, either enhancing or attenuating it depending on the array configuration. This interaction was characterized using a resonant solidity that combines roughness density with the scales imposed by the resonance frequency and spanwise micropillar spacing. From a sensing perspective, the micropillars responded distinctly to different scales of the flow: small-scale turbulence excited resonant motion, while large-scale outer-layer structures were superimposed on this motion and simultaneously modulated the amplitude of the resonant response. These results demonstrate a coupled interaction in which the micropillars both respond to and modify the surrounding turbulence, offering a dynamic yet passive pathway for flow control.

Bio:

Ebenezer P. Gnanamanickam is a Professor in the Embry-Riddle Aeronautical University, Department of Aerospace Engineering with an M.S. and Ph.D. in Aeronautics and Astronautics from Purdue University. Following his doctorate, he served as a visiting assistant professor at Purdue University and a postdoctoral fellow in the Department of Mechanical Engineering at the University of Melbourne, Australia. His research focuses on turbulent flow interactions, encompassing fundamental physics, novel flow control strategies, applied aerodynamics, and associated measurement techniques. A former AFOSR Young Investigator awardee, his work has been supported by NSF, the Army Vertical Lift Center of Excellence, ARO, and AFOSR. He has graduated six doctoral students and is currently advising three more.

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