HARNESSING FLOW-INDUCED FLUTTER OF FLAPPING FLAGS FOR HEAT TRANSFER, MIXING, AND ENERGY HARVESTING

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Date
2019-07-16
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Johns Hopkins University
Abstract
Fluid-structure interaction is ubiquitous in natural and engineering systems. While in engineering applications, these aeroelastic phenomena have historically been considered as detrimental, in Nature there are widespread instances of biological systems designed specifically to take advantage of fluid-structure interaction phenomena. This research explores the notion of utilizing fluid-structure interaction to achieve a range of engineering objectives. In particular, we look at flow-induced flutter of highly flexible bodies such as flags, membranes, and filaments. We use fully-coupled fluid-structure interaction (FSI) CFD simulations to first explore two related engineering applications: heat transfer enhancement in forced-convection channel-flow heat exchangers, and mixing enhancement in low Reynolds number micromixers operating in the inertial microfluidic regime Re=O(1-100). In both applications, we show that the addition of a flapping membrane into a channel (or duct) flow can dramatically improve system performance for either heat transfer or mixing. Simulations are used to explore the flow physics underlying this improvement in performance. We then explore the use of inverted flags (flags where the leading edge is free, and the trailing edge is fixed) to harvest energy via flow-induced flutter. This study focuses on the use of multi-flag arrangements as a way to improve overall system performance. We also describe the design, fabrication and testing a 1ftx1ft cross-section low-Reynolds number (maximum speed of 20 m/s) wind tunnel which was developed in provide comprehensive validation data for the FSI simulations.
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Keywords
Fluid-Structure Interaction, Flow-Induced Flutter, Computational Fluid Dynamics, Microfluidics
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