EXPERIMENTAL INVESTIGATION OF THIN-WALLED CYLINDRICAL CANTILEVER BEAMS UNDERGOING VORTEX-INDUCED VIBRATIONS

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2024

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The main objective of this Master’s thesis is to present the execution and results of an experimental study on the dynamic response of three low-mass ratio cylindrical cantilever beams experiencing vortex-induced vibrations. The tested cylinders are hollow, sealed, and made out of polycarbonate with low mass ratios m* of 0.761, 0.830, and 0.922 and damping ratios between 0.037, 0.051, and 0.045. The motion is being analyzed by using high-speed cameras to document the motion under UV lights for better image quality. ProAnalyst software is being used to translate the videos into motion-tracking data in two directions In-Line (IL) and Cross-Flow (CF). Our findings indicate that the IL: CF frequency ratios conform to the conventional 2:1 frequency ratio. Nonetheless, we also observed 1:1 and 3:1 frequency ratios at low and high reduced velocities, accompanied by predominantly small positive and negative lift coefficients in phase with velocity values. The amplitude response aligns with previous literature, although our study shows that the in-line amplitudes reach higher values due to the cylinders’ low mass and damping ratios. Specifically, at reduced velocities below 3, one of the cylinders experienced higher in-line amplitudes than cross-flow.

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Ocean engineering, Cantilever Cylinder, Fluid Body Interaction, Low-Damping Ratio, Low-Mass Ratio, Ocean Structures, Vortex-Induced Vibrations

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90 pages

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