Hydrodynamic Analysis and Shape Optimization for Vertical Axisymmetric Wave Energy Converters

• Published in: China ocean engineering Vol. 30; no. 6; pp. 954 - 966
• Main Author: 张万超 刘恒序 张亮 张学伟
• Format: Journal Article
• Language: English
• Published: Nanjing Chinese Ocean Engineering Society 01.12.2016; Springer Nature B.V; College of Shipbuilding Engineering, Harbin Engineering University, Harbin 150001, China
• Subjects: Coastal Sciences; Converters; Cylindrical waves; Damping; Energy conversion; Engineering; Fluid- and Aerodynamics; Hydrodynamic coefficients; Marine & Freshwater Sciences; Mathematical models; Numerical and Computational Physics; Oceanography; Offshore Engineering; Radiation; Shape optimization; Simulation; Stepped; Velocity; Velocity potential; Wave energy; Wave excitation; Wave power; complex wetted surface; vertical axisymmetric; geometrical shape; astringency; semi-analytical method
• ISSN: 0890-5487; 2191-8945
• DOI: 10.1007/s13344-016-0062-2

The absorber is known to be vertical axisymmetric for a single-point wave energy converter （WEC）. The shape of the wetted surface usually has a great influence on the absorber＇s hydrodynamic characteristics which are closely linked with the wave power conversion ability. For complex wetted surface, the hydrodynamic coefficients have been predicted traditionally by hydrodynamic software based on the BEM. However, for a systematic study of various parameters and geometries, they are too multifarious to generate so many models and data grids. This paper examines a semi-analytical method of decomposing the complex axisyrnmetric boundary into several ring-shaped and stepped surfaces based on the boundary discretization method （BDM） which overcomes the previous difficulties. In such case, by using the linear wave theory based on eigenfunction expansion matching method, the expressions of velocity potential in each domain, the added mass, radiation damping and wave excitation forces of the oscillating absorbers are obtained. The good astringency of the hydrodynamic coefficients and wave forces are obtained for various geometries when the discrete number reaches a certain value. The captured wave power for a same given draught and displacement for various geometries are calculated and compared. Numerical results show that the geometrical shape has great effect on the wave conversion performance of the absorber. For absorbers with the same outer radius and draught or displacement, the cylindrical type shows fantastic wave energy conversion ability at some given frequencies, while in the random sea wave, the parabolic and conical ones have better stabilization and applicability in wave power conversion.