Interaction between coherent fluid structures and highly compliant smart materials: towards small-scale energy harvesting

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The increasing demand for lightweight, rechargeable, robust microelectronic devices has spawned considerable interest in small-scale energy harvesting sources and methodologies. An environmental energy source that has received relatively little scientific attention is coherent fluid structures, such as vortex rings and flow in the wake of a object. Vortex rings, a simple example of which is a "smoke ring" blown out of the mouth, occur in such varied places as the ventricles of the mammalian heart and in the wake of a swimming fish. Harvesting energy from coherent fluid structures can be accomplished using cantilevered beams constructed from highly deformable electro-active smart materials. Such materials generate an electrical response when deformed, thus they provide a method to directly convert mechanical energy, in the form of the fluid kinetic energy, into usable electrical energy. Efficiently harvesting energy from the coherent fluid structure/smart material-based cantilever necessitates that the interaction between the fluid and the structure be well understood. To date, research into the interplay between vortex rings (selected since they are well characterized mathematically and simple to produce experimentally) and mechanical structures has largely been limited to rigid planar walls. In the current case, the mechanical structure is capable of large time-varying deformations, which dramatically change the dynamics of the problem. The proposed research will consist of two phases; Phase I will be an extensive study of the complex problem of a vortex ring interacting with a highly deformable cantilever beam, while Phase II will focus on the energy harvesting aspects, including optimizing the power generation via a parametric study of the critical parameters, such as the material rigidity and angle of impact. The proposed research program has both fundamental and practical applications. The fundamental knowledge gained from studying the fluid/smart material interaction problem will be of increasing importance as smart materials continue to integrate into daily life. Of more immediate impact is the energy harvesting aspect of the study, which will aid in the design and development of long operating life sensors and microdevices.