Computation of vortex-induced vibrations of long structures using a wake oscillator model: Comparison with DNS and experiments

We consider here the dynamics of flexible slender systems undergoing vortex-induced vibration (VIV). This type of motion results from the coupling between the oscillating wake due to cross-flow and the structure motion. Practical application, are mainly found in the field of ocean engineering, where long flexible structures such as risers or mooring cables are excited by sea currents. The wake dynamics is here represented using a distributed wake oscillator coupled to the dynamics of the slender structure, a cable or a tensioned beam. This results in two coupled partial differential equations with one variable for the solid displacement and one for the wake fluctuating lift. This simplified model of the wake dynamics has been previously validated on simple experiments. Here, comparisons with direct numerical simulation results are done for both uniform and non-uniform flow. Comparison is also performed between the wake oscillator predictions and some experimental results on long cables. The results of those comparisons show that the proposed method can be used as simple computational tool in the prediction of some aspects of vortex induced vibrations of long flexible structures. (c) 2006 Elsevier Ltd. All rights reserved.