Fluid-structure coupled analysis of flow-induced vibrations in three dimensional elastic hydrofoils

Abstract

Hydrofoils have been widely used in ocean and offshore structures. The research on their elastic response in turbulent flow is quantitatively challenging, and it is of great interest for consideration in engineering applications. In this study, a fluid-structure coupling numerical simulation of a three-dimensional elastic hydrofoil is performed. The SST (shear stress transfer) k-ω turbulence model is used to simulate the vortex shedding and near-wall flow characteristics with different Reynolds numbers. By coupling the FVM (finite volume method), the elastic response of the hydrofoils is analyzed. Furthermore, the formation and evolution of the trailing vortex is described. The elastic vibration and subsequent stress distribution of the hydrofoil caused by the vortex shedding are investigated. Moreover, the frequency domain characteristics of the vibration and turbulence field are analyzed. The results show that resonance occurs when the frequency of the vortex induced flow field fluctuations matches the natural frequency of the hydrofoil. This leads to intense hydrodynamic fluctuations in the time domain. In addition, the dynamic responses of the hydrofoil will “lock-in” to its natural frequency within a certain range of flow velocities. Although the frequency lock-in is often accompanied by resonance, lock-in phenomena cannot be solely attributed to resonance, which is caused by hydrofoil switching between the free and forced vibration regimes. The frequency lock-in is caused by the dominant frequency modulation induced by the fluid motion, thus, it can exert non-negligible effects on the flow field via fluid-structure coupling.