Numerical studies and proposal of design equations on cylindrical oscillating wave surge converters under regular waves using SPH

Abstract

An oscillating wave surge converter extracts energy from sea waves and converts it into electricity. Its main components are a flap, hinge, base, and power take-off system. In this paper, an oscillating wave surge converter comprising a cylindrical flap, made up of several cylinders, is numerically investigated under regular waves using the smoothed particle hydrodynamics method. A comparison between cylindrical and box-type rectangular flaps is performed firstly, in which the former extracts more energy and is more suitable in bearing water pressures than the latter. Subsequently, the effects of five parameters (load conditions, total flap mass, hinge height from the seabed, damping of the power take-off system, and the flap thickness) are systematically examined. To investigate the effects of motion resonance, the natural periods of the structures are also studied. Meanwhile, correlation, partial correlation, and linear regression analysis are conducted to obtain a detailed understanding of the effects of the parameters. The details about how to apply the conclusions to full scale model or even real sea states are discussed also. Numerical results show that the heavier and thinner the flap, or the higher the hinge, the better the wave-absorption performance will be. As the damping increases, the extracted energy increases initially and then decreases. Wave conditions contribute the most to wave absorption and are the key parameter in the designs of the converters, followed by hinge height, damping, thickness, and mass of the flap. Motion-resonance also benefits the wave-absorptions. The proposed equations in the linear regression analysis all show high statistical significance level, which can be regarded as reference when designing this kind of converters, accelerating the design process.