Energy Balanced Double Oscillator Model for Vortex-Induced Vibrations
Publication: Journal of Engineering Mechanics
Volume 125, Issue 3
Abstract
An improved theoretical basis is developed for representation of vortex-induced oscillations of structural elements by models consisting of two coupled oscillators. The mutual forcing terms are based on exact transfer of energy from the fluid to the structural oscillator. This leads to a system with distinct frequency locking and resonance when fluid and structural natural frequencies are similar. The present work implements a simple quadratic fluid damping, but more general fluid damping can be introduced without changing the basic features of the model. The response curve for stationary oscillations consists of two distinct branches, separated by jumps in frequency, amplitude, and phase closely resembling experimentally observed free vortex-induced vibrations. A stability analysis shows that the final part of each branch is unstable, and a transient analysis illustrates the transition between the two modes of oscillation for slowly increasing or decreasing fluid velocity through the lock-in region. Model calibration is discussed and parameters are identified representing available experimental data for lock-in frequencies and resonance amplitudes for systems with relative structural damping in the interval 1.5–3.0 × 10−3 and different values of the mass ratio.
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Published In
Journal of Engineering Mechanics
Volume 125 • Issue 3 • March 1999
Pages: 263 - 271
History
Received: Jan 26, 1998
Published online: Mar 1, 1999
Published in print: Mar 1999
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