Numerical study on the optimization design of the conical bottom heaving buoy convertor

Abstract

Heaving buoy convertor is one of the most common wave energy convertors (WECs) for its brief structure form and adaptability to wave directions. In reality, some heaving buoy convertors are designed to combine with other marine structures like floating platform, seawall and offshore wind turbine. In such cases, the budget or the installation space may be a limitation for buoy's characteristics. Therefore, the choices of dimension and mass are of great importance to capturing as much as possible energy under the limited condition. However, in the optimization of the buoys, this study, about the effects on the hydrodynamic performance and energy output by the relationship between section surface, mass and draft, is not sufficient. This paper studies the optimization design of a conical-bottomed heaving buoy converter with consideration of Power Take-Offs (PTO) which are linear, constant, and quadratic non-linear. A 3D numerical wave tank (NWT) based on the RANS equations and two-phase VOF model is established using CFD software Flow-3D. The numerical model is applied to deal with the buoy's movement under different PTOs, and is validated by the experimental data. The movements of a conical-bottomed heaving buoy with different mass and section surface 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 buoy prototype optimization design under the certain wave conditions.