Hydrodynamic Response of One-Body and Two-Body Point Absorber Coupled with Catenary and Taut Mooring Lines in Low Wave Condition

Abstract

Wave energy converter (WEC) must sustain the cyclical loads and motions formed by the contact of the wave load and the WEC's motions in the random elevation of the sea surface when coupled with mooring lines. In a previous study, a simulation model for the tension of the mooring lines was established and validated; this study examines the point absorber heaving motions in response to the mooring lines. The purpose of this paper is to provide a method for simulating heaving motions that is suitable for a complete examination of the heave motion response of the device, coupled with mooring lines to the bottom using a one-body and two-body point absorber. The case study is a cylindrical floating-point absorber with one, two, three, and four distributed mooring lines configured in catenary or taut configuration. The dynamics of the point absorber are simulated and analysed in the time domain utilising various mooring line configurations by Computational Fluid Dynamics (CFD) software modelling methodologies. A detailed response analysis is conducted on a Malaysian low wave condition in shallow water, and the results are compared for one and two-body point absorber systems. The modelling procedure using a two-body with four mooring lines is indicated as the ideal method for capturing the interaction between the WEC system's components, which has been proved to be crucial for evaluating heave response. The average heaving response of four mooring lines with catenary configuration is preferred since it indicates the device's heaving response in comparison to others. The results indicated that a two-body point absorber Response Amplitude Operator (RAO) is more efficient at absorbing low wave heights in four catenary mooring lines configurations. The two-body point absorber outperformed the single-body point absorber in all wave conditions.