Hydrodynamic performance optimization of a cost-effective WEC-type floating breakwater with half-airfoil bottom

Abstract

Aiming to design and develop an affordable integrated floating breakwater and wave energy converter (WEC) system that has high performance in power absorption and wave attenuation, a novel integrated floater with a half-airfoil bottom is proposed. The genetic algorithm combined with the boundary element method is employed to optimize the half-airfoil bottom surface represented by the class-shape function transformation parameterization method, for maximizing the power density over the operating bandwidth. Then the operating performance of the optimal half-airfoil bottom floater is further studied in a validated two-dimensional viscous numerical wave tank. The result shows that the optimal half-airfoil bottom floater is a more effective and affordable solution than square and triangular bottom ones. The effective ratio of the floater breadth to the wavelength can be reduced to about a tenth, far below that of the conventional floating breakwater, denoting its excellent wave attenuation capability. The increase in floater breadth induces more intense vortex dynamic behaviors and thus higher dissipation coefficient. A shallow front-wall draft design can improve the maximum conversion efficiency to more than 74%, slightly broaden the resonance bandwidth, and reduce energy dissipation while minimizing costs. The nonlinear PTO damping force contributes to a more stable response. The research results denote the feasibility of bio-inspired WEC-type floating breakwaters and show their superiority in energy extraction, wave attenuation, as well as cost reduction.