The Vortex/Structure Dance: Exploring Coupled Interactions for Energy Harvesting and Speech Modeling Applications

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Vortices abound in nature, appearing in fields ranging from aerodynamics (wing tip vortices) to propulsion of aquatic animals (fish and jellyfish) to vortex shedding in the larynx during human phonation. While vortex dynamics has been studied extensively for decades, examining and exploiting the interaction of vortices with deformable/active structures for flow control, energy harvesting, and bio-inspiration/biomimicry has reinvigorated the field. This proposal focuses on two seemingly disparate but intimately related areas of importance in engineering and medicine: namely, small-scale fluidic energy harvesting using deformable smart-materials for powering micro-electronic devices, including remote sensing networks; and understanding and modeling vocal fold mechanics in human speech with the long term goal (10+ years) of aiding in surgical planning for pathology remediation. The shared core mechanics of these two research tracks is the bi-directional coupling of a vortex-laden fluid flow with a compliant surface; that is, the surface (either the energy harvester or the vocal fold tissue) deforms due to the pressure field in the adjacent fluid flow, which, in turn, alters the fluid boundary condition. As such, this research program envisions establishing a thorough and fundamental understanding of the interaction of vortices with deformable structures via a mix of theoretical analysis, computational modeling, and experimental testing and validation for advancing understanding of energy harvesting and speech modeling. This research program will focus on the development of tools applicable to both research foci, as well as the track-specific implementation of these tools for addressing field-specific research questions. Initial model development will focus on (two-dimensional) vortex dipoles and (three-dimensional) rings (i) passing over a compliant bed and relating the pressure field and frequency of the vortices to the time-variant wall deformation; and (ii) impacting a compliant structure at various angles and exploring the impact mechanics. The governing dimensionless parameters will be varied parametrically and the importance of three-dimensional phenomena, such as edge effects on the structure and vortex stretching during impact and subsequent vortex breakdown, will be explored.  To ensure problem-specific outcomes, the energy harvesting track will focus on development and validation of energy harvesting devices and evaluation of the optimal parameters and performance criteria for maximizing energy extraction, while the speech track will investigate the impact of vortices passing through the vocal tract on the self-sustained oscillations of the vocal folds for both symmetric and asymmetric tissue properties. This project will lead to optimized smart material-based energy harvesting devices and improved speech models incorporating vortex effects.