Date of Award

8-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

LI, GANG

Committee Member

DAQAQ , MOHAMMED

Committee Member

THOMPSON , LONNY

Abstract

An energy harvesting system inspired by musicplaying harmonicas was developed for microwind power generation. The energy harvester uses flow-induced self-sustained oscillations of a piezoelectric beam embedded within a chamber to generate electric power. While the power generation capability of the energy harvester has been demonstrated previously, there is a lack of understanding behind the basic physics of the driving mechanism responsible for the self-sustained oscillations. In addition, the performance of the nonlinear multi-physics system with strong fluid and structure coupling depends on many physical and design parameters. A systematic study on the effects of these parameters is necessary for the design and optimization of the energy harvester.
To address these issues, this study focuses on the modeling and finite element analysis of fluid-structure interaction in the wind energy harvester. A full 3-D finite element model is constructed for the device. The fundamental mechanism of the fluid-structure interaction in the device that results in the self-sustained beam vibration is investigated. It is found that the compressibility of the fluid is the key factor. The result indicates that the beam vibration in the wind energy harvester cannot be sustained in incompressible fluids. By using the finite element model, the effects of a set of physical and design parameters, such as the fluid viscosity, chamber volume, side gap and configuration of the beam at the outlet, are studied. Based on the numerical analysis results, a new design of the beam is proposed to obtain a larger deflection of the beam under the given air pressure in the chamber. The increase of the beam deflection will induce a larger strain in the piezoelectric layer and a larger output voltage of the energy harvester, which is desired in many applications.

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