Date: Friday, February 15, 2013
Location: 1084 East Hall (3:00 PM to 4:00 PM)
Title: Cantilever beams in axial flows: flutter Instabilities, post-critical dynamics, scaling laws, and energy harvesting applications
Abstract: Structures may lose their stability if exposed to external flows; a very famous example of this is the collapsed Tacoma Narrows Bridge in 1940. Accordingly, proper designs should ensure the stability of exposed structures to avoid failure or permanent deformations. However, there are many cases where flow exerted deformations on solids might be desired. Examples include energy harvesting applications where the fluid induced deformations might be converted to electricity through electroactive polymers (EAP), as well as the use of flexible lift-generating surfaces, such as propeller blades, hydrofoils, that might perform better in off-design operating conditions than their rigid counterparts.
The first part of this talk presents the current results of our studies on the dynamics of two-dimensional cantilevered beams in incompressible, viscous fluid flows. The solution method involves solving the Navier-Stokes equations for the fluid using a fractional-step method and the Kirchhoff-Love equations for the beam and coupling the fluid and solid dynamics with Peskin's Immersed Boundary method. The results include identifying the critical non- dimensional parameters, identifying the flutter stability boundary, and classifying the different vorticity shedding patterns and beam oscillation modes as a function of these critical parameters. The second part of this talk focuses on piezoelectric cantilever beams and their use to harvesting energy under flutter conditions. The electromechanical coupling brings on two additional critical parameters in terms of a non-dimensional energy conversion and electric damping coefficient. The talk will conclude on assessing the feasibility of applying two-different scaling laws onto this system: the Reynolds number (Re) and Mach number (Ma) scale. It will be shown that designing reduced-scale experiments with Re scaling brings various difficulties (impossibilities) mostly due to material selection issues, while the Ma scaling is very favorable for moderate to high Re operating conditions. This is a joint work with Prof. Yin Lu Young.
Speaker: Deniz Akcabay
Institution: Naval Architecture and Marine Engineering, University of Michigan
Event Organizer: Silas Alben alben@umich.edu
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