The Influence of Tidal Unsteadiness on a Tidal Turbine Blade Flow-Induced Vibration

The influence of unsteady tidal flow on the flow-induced vibration of a vertical axis tidal turbine blade is investigated numerically in this paper. A 2D CFD model is developed to simulate the blade flow-induced vibration in OpenFoam. The vibration is caused by dynamic loading from the unsteady tide. It is recognized that the unsteady tidal current mainly comes from the changes in tidal velocity magnitude and angle of attack experienced by a tidal turbine blade as it rotates. This paper studies numerically how velocity magnitude and initial angle of attack influence tidal turbine blade vibrations and the effects of the velocity and angle of attack are evaluated separately where the unsteadiness parameters are varied around a set of environmental condition. The vibration is examined through time histories of blade displacement, pressure distribution on the blade surface and the tidal current regime. The blade is assumed to have pitch and heave responses thus the vibration is in the form of transverse and torsional vibrations. The results show that increasing tidal velocity magnitude strengthens the torsional vibration. The increase of angle of attack is likely to generate chaotic motions and enhance both transverse and torsional vibrations.