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

对轻质、可充电、坚固耐用的微电子设备的需求日益增长，这引发了人们对小规模能源收集来源和方法的极大兴趣。一种相对较少受到科学关注的环境能源是连贯的流体结构，如涡环和物体尾流。涡旋环的一个简单例子是从嘴里吹出的“烟环”，它出现在哺乳动物心脏的脑室和游动的鱼的尾巴上。从连贯的流体结构中获取能量可以使用由高度变形的电活性智能材料构建的悬臂梁来完成。这种材料在变形时会产生电响应，因此它们提供了一种将机械能以流体动能的形式直接转换为可用电能的方法。要有效地从连贯的流体结构/智能材料悬臂梁中获取能量，就必须很好地了解流体和结构之间的相互作用。到目前为止，对涡环(选择它们是因为它们在数学上具有很好的特性，并且易于实验制造)和机械结构之间的相互作用的研究在很大程度上局限于刚性平面墙。在目前的情况下，机械结构能够产生大的时变变形，这将极大地改变问题的动力学。拟议的研究将分为两个阶段；第一阶段将广泛研究涡环与高度变形的悬臂梁相互作用的复杂问题，而第二阶段将专注于能量收集方面，包括通过对关键参数(如材料刚度和冲击角)的参数研究来优化发电。提出的研究方案具有基础性和实践性。随着智能材料不断融入日常生活，从研究流体/智能材料相互作用问题中获得的基本知识将变得越来越重要。更直接的影响是这项研究的能源收集方面，这将有助于设计和开发长工作寿命的传感器和微型设备。

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.