It is known theoretically [1–3] that infinitely long fluid loaded plates in mean flow exhibit a range of unusual phenomena in the ‘long time’ limit. These include convective instability, absolute instability and negative energy waves which are destabilized by dissipation. However, structures are necessarily of finite length and may have discontinuities. Moreover, linear instability waves can only grow over a limited number of cycles before non-linear effects become dominant. We have undertaken an analytical and computational study to investigate the response of finite, discontinuous plates to ascertain if these unusual effects might be realized in practice. Analytically, we take a “wave scattering” [2,4] — as opposed to a “modal superposition”  — view of the fluttering plate problem. First, we solve for the scattering coefficients of localized plate discontinuities and identify a range of parameter space, well outside the convective instability regime, where over-scattering or amplified reflection/transmission occurs. These are scattering processes that draw energy from the mean flow into the plate. Next, we use the Wiener-Hopf technique to solve for the scattering coefficients from the leading and trailing edges of a baffled plate. Finally, we construct the response of a finite, baffled plate by a superposition of infinite plate propagating waves continuously scattering off the plate ends and solve for the unstable resonance frequencies and temporal growth rates for long plates. We present a comparison between our computational results and the infinite plate theory. In particular, the resonance response of a moderately sized plate is shown to be in excellent agreement with our long plate analytical predictions.
- Fluids Engineering Division
Fluid Structure Interaction With Mean Flow: Over-Scattering and Unstable Resonance Growth
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Arzoumanian, S, & Peake, N. "Fluid Structure Interaction With Mean Flow: Over-Scattering and Unstable Resonance Growth." Proceedings of the ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASME 2010 7th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, and Flow-Induced Vibration and Noise: Volume 3, Parts A and B. Montreal, Quebec, Canada. August 1–5, 2010. pp. 1055-1062. ASME. https://doi.org/10.1115/FEDSM-ICNMM2010-31170
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