UNS: The Interaction of Coherent Structures in a Shear Layer with a Flexible Beam

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1511761(Erath)The goal of this proposal is to investigate experimentally and numerically the fluid structure interaction when fluid passes around a flexible beam. This is a representative model of air flow past the vocal cords. The study will focus not only on conditions representing healthy vocal cords, but mainly on cases where the vocal cords are not healthy. Results from the proposed research can, thus, impact speech rehabilitation and could be felt by many people among the roughly 30% of the population of the US, who are estimated to suffer voice pathology at some point in their lives.The main objective of the proposed research is to identify the mechanisms by which a train of vortices advecting over a flexible beam incite motion in the structure, and parametrically explore this fundamental fluid- structure interaction problem. It is proposed to quantify how vortices produced during speech impact vocal fold dynamics in both normal, as well as pathological speech. Currently, there is incomplete understanding of the interplay between the aerodynamic loading as air comes to the vocal cords and the structural response of the tissue. This deficiency will be addressed by experimentally and theoretically/numerically investigating vortex-beam interactions that arise from coherent structures passing over a flexible beam. The hypothesis is that the coherent vortical structures are formed from the Kelvin-Helmholtz instability in the shear layer of the flow. The excitation of the beam will be investigated over a range of nondimensional beam, fluid, and geometrical parameters. The experimental results will validate the theoretical flow model of vortex-beam interactions, which will then be used to extend and explore the parameter space beyond the limitations of the experimental facility. The theoretical model will ultimately be applied to a numerical model of voiced speech to quantify the role of vortex-tissue interactions on vocal outcomes. The fundamental problem of vortices interacting with a deformable surface also has specific relevance to the topic of using deformable electroactive devices to harvest energy from fluids. In addition to graduate and undergraduate student education, a plan for K-12 outreach is proposed, where the PI will partner with high school choir directors to provide classroom demonstrations relating voice and singing to science.