Effect of harmonic inflow perturbation on the two-degree-of-freedom vortex-induced vibration of a cylinder
Date
2022-12-09
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Abstract
The wake dynamics, structural response, and their coupling are investigated for a circular cylinder undergoing vortex-induced vibration (VIV) near a plane boundary at Re = 200. The effects of inflow perturbations on the structural response are explored, and three regimes of response that do not occur for VIV in a uniform flow have been identified. It was found that the interaction of a symmetric instability via perturbations in the wake and natural instabilities in the wake is the underlying physical mechanism resulting in the presence of the newly identified regimes of response. In Regime I, high drag values were observed; however, the amplitudes of vibrations remain close to the unperturbed case. Regime II is a high excitation regime characterized by a highly modulated response. In Regime III, the natural shedding mode and its second harmonic are reinforced by perturbations. In this Regime, sub-harmonic resonance occurs, resulting in irregular wake dynamics and a highly excited structural response. Regimes II and III fundamentally alter the coupling mechanism between the wake dynamics and cylinder response. To capture the observed dynamics in these regimes as well as the unperturbed response, a new approach to VIV modeling is proposed. In particular, a coupled structural response and wake dynamics system are modeled for the first time using non-isochronous oscillators. The inter-dependency of the oscillation amplitude and frequency of oscillations, and frequency entrainment are identified as the main characteristics of the flow that this model can capture.
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vortex-induced vibration
Citation
Hassanpour, M. (2022). Effect of harmonic inflow perturbation on the two-degree-of-freedom vortex-induced vibration of a cylinder (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.