Coupled motion-mooring-power dynamics in a multi-buoy floating wave energy converter under shallow marginal-sea conditions

A multi-buoy floating wave energy converter is analyzed numerically to understand its motion response, mooring tension, power output, and capture width ratio (CWR) under varying ocean parameters. In the STAR-CCM+ system, a three-dimensional numerical wave tank is constructed, employing the VOF method and the SST k-ω turbulence model. This model is then validated against the published roll-decay data. Wind velocity (V), current velocity (U), wave height (H), and water depth (D) are analyzed in the range of the Yellow Sea and Bohai Sea. Results indicate that wave period dictates the dynamic response: longer wave periods cause increased heave and surge motions, but also reduce the power output and CWR. This shows that energy capture relies on relative buoy motion, not absolute motion amplitude. Current velocity has a period-dependent effect, enhancing power output under short-period waves but weakening energy capture under longer-period waves. Wave height is the main factor, but once a deep-water-like response is achieved, water depth has limited influence. Orthogonal range analysis shows that the influence on power output decreases in the order of H, V, U, and D. The main-effect-based favorable combination is V = 6.5 m/s, U = 0.8 m/s, H = 1.8 m, and D = 35 m, whereas the highest power among the 25 simulated cases reaches 9395.86 W under the same wind velocity, wave height, and water depth but at U = 0.4 m/s.