Numerical Study on the Power Take-Off Effects of the Heaving Buoy Convertor

Heaving buoy convertor is one of the most common wave energy convertors (WECs) for its brief structure form and adaptability to all wave directions. To describe the motion of the heaving buoy in analytic method, the linear power take-off (PTO) type is usually adopted. However, the PTO types are diverse in reality and have different effects on the motion of the heaving buoy. This paper discusses different PTO types including linear, constant, and quadratic non-linear PTO, which are frequently adopted or may exist in reality. A 3D numerical wave tank (NWT) based on the RANS equations and two-phase VOF model was established using CFD software Flow-3D. The numerical model is capable of dealing with the buoy's movement under different PTO types, and is validated by the experimental data. The movements of the heaving buoy under three different PTOs are studied numerically, which provide more information of the effects on the energy capture performance. The conclusion of this paper gives a guidance to the choice of PTO type in heaving buoy convertor's design.