Abstract: To clarify the power capture influence of the submerged depth for the three-degree-of-freedom(3-DOFs)oscillating buoy wave energy converters, two floating and submerged buoy models were established. Power capture characteristics of the submerged buoys were calculated and compared with different depths and wave conditions. The cylindrical buoy was selected. The submerged depth were 0.5, 1.0, 1.5 and 2.0 times of the buoy’s height. The mass of the buoys were the same. The floating buoy was selected as a comparison. Based on linear potential theory and boundary element method, the hydrodynamic model was established, and the hydrodynamic parameters and kinematic responses of the buoy were calculated. And the optimal average output powers were calculated with linear power take-off(PTO)damping. The effect of submerged depth on the power capture of the buoy was analyzed. The results showed that increasing the submerged depth could reduce buoys wave excitation forces and power absorption. For 3-DOFs buoy, the floating one had a better power capture performance under low frequency waves, while the submerged one with a small submerged depth was better under high frequency waves.

Key words: wave energy, oscillating buoy, multi-freedom buoy, power capture, hydrodynamic characteristic