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Title:Fluid-structure interaction of a cantilevered plate in supersonic separated flow
Author(s):Bojan, Griffin Kenji
Advisor(s):Dutton, Craig
Contributor(s):Elliott, Gregory
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):fluid-structure interaction
supersonic
cantilevered plate
compressible flow
Abstract:The study of fluid-structure interaction (FSI) is one of ever-increasing importance as high-speed aircraft continue to reach higher Mach numbers. Research into high-speed FSI is especially critical with respect to control surfaces that may become compliant at these high Mach numbers. In collaboration with similar efforts at The Ohio State University and the University of Tennessee Space Institute, recent studies at the University of Illinois at Urbana-Champaign (UIUC) have focused on the FSI of a cantilevered plate geometry in Mach 2 flow. The geometry of interest, representative of a compliant control surface, consists of an overhanging plate that extends past the edge of a backward-facing step to create a separated region in the supersonic flow. This setup allows for the study of recirculation effects and unsteady pressure forcing on the cantilevered plate in the absence of shock-boundary layer interactions that would be present if the plate were inclined to the flow. The height of the cavity has been chosen such that it corresponds to the height of a flap of equal length deflected at 20 degrees. Both rigid and compliant variations of the cantilevered plate have been studied in order to capture the fluid response with and without structural deformation. These geometries have been studied at fully started wind tunnel conditions, as well as during tunnel startup when the unsteady flow elicits a highly dynamic response from the flexible plate. High-speed schlieren visualization, high-frequency pressure transducer measurements, oil flow visualization and planar particle image velocimetry (PIV) measurements have been used to characterize the flow around both geometries. Stereo digital image correlation (sDIC) was used to capture time-resolved surface deflection measurements for the flexible plate. The data show the presence of distinct frequencies in the pressure fluctuations beneath the rigid plate and a very strong correlation between cavity pressure fluctuations and plate deflection in the case of the flexible plate. PIV velocity measurements show similar results between the rigid and compliant geometries in the flow outside the recirculation region but reveal several differences in the cavity flowfields, though some of these could be linked to three-dimensional facility effects. Spectral analysis of the sDIC results revealed several distinct frequencies present in the dynamic response of the flexible plate, and modal decomposition showed that the strongest of these frequency peaks always corresponded to the same four mode shapes.
Issue Date:2021-07-22
Type:Thesis
URI:http://hdl.handle.net/2142/113082
Rights Information:Copyright 2021 Griffin Bojan
Date Available in IDEALS:2022-01-12
Date Deposited:2021-08


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