CFD Simulation of a Passively Controlled Point Absorber Wave Energy Converter

Recently CorPower Ocean AB presented laboratory tests of a point absorber wave energy converter equipped with a novel technique for passive phase control. The technique, known as WaveSpring, widens the response bandwidth by a negative spring arrangement, and in the tank experiment an up to threefold increase in delivered power as compared to pure linear damping was observed. As previously reported, for point absorbers close to resonance, the use of standard radiation-diffraction models can become unreliable while CFD simulations accurately capture the nonlinear wave height dependent response. Thus, in the present study a module representing the WaveSpring technology was implanted in the OpenFOAM framework and CFD simulations of the buoy were performed both with and without the WaveSpring module. Good agreement between simulated and experimental results was observed, and the WaveSpring behavior was well captured in the numerical simulation. The CFD model can be used for further tuning of the WaveSpring/buoy design as well as providing validation data for radiation-diffraction models.