Design considerations for a three-tethered point absorber wave energy converter with nonlinear coupling between hydrodynamic modes

• Published in: Ocean engineering Vol. 254; p. 111351
• Main Authors: Tran, N., Sergiienko, N.Y., Cazzolato, B.S., Ghayesh, M.H., Arjomandi, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-06-2022
• Subjects: Coupling between hydrodynamic modes; Hydrodynamic nonlinearities; Multi-mode wave energy converter; Weak-scatterer modelling; WEC design; Weak-scatterer modelling; Coupling between hydrodynamic modes; Hydrodynamic nonlinearities; WEC design; Multi-mode wave energy converter
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2022.111351

Multi-mode Wave Energy Converters (WECs) are designed to harvest energy simultaneously from multiple hydrodynamic modes, thereby maximising power absorption. The behaviour of each mode must be carefully considered, given that hydrodynamic and geometric coupling between modes can lead to severe reductions in power if improperly designed. This study aims to investigate how the design of a planar three-tethered WEC can be used to tune the surge, heave and pitch hydrodynamic modes to achieve maximum power absorption. The effect of various tether arrangement and mass distribution design parameters on the performance of a WEC subjected to both geometric and hydrodynamic nonlinearities was investigated. Results indicated that, to absorb the most power in regular waves, the tether configuration should be adjusted such that the surge and heave dominant rigid body modes are resonant with the incident wave. Geometric nonlinearities associated with the tether arrangement were found to cause sub-harmonic excitations which severely compromised device performance, with further reductions in power when nonlinear hydrodynamics were considered. In irregular waves, the optimal design became more strongly driven by performance in surge. Overall, maximum power was achieved when all three tethers were attached close to one another on the bottom of the buoy.
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•Tether arrangement design parameters have the greatest effect on device performance.•Changing mass distribution design parameters gives little benefit to power absorbed.•Optimal performance when surge and heave dominant rigid body modes are resonant.•Geometric nonlinearities can result in sub-harmonic excitations which reduce power.•Converter design is more strongly driven by surge performance in irregular waves.