Bionic Raft Design and Performance Investigation of a Two-Raft Wave Energy Converter

This paper proposes a two-raft wave energy conversion technology with bionic rafts, aiming to enhance the wave energy capture performance of existing devices with regularly shaped rafts. The cross-sectional shape of the bionic raft is designed as a nested pattern of the long and short axes of two semi-ellipses, which is inspired by the cross-sectional shape of the flat shark. Based on the computational fluid dynamics (CFD) model of the wave energy converter (WEC) with the bionic raft in waves, it is verified that the designed bionic raft positively enhances the wave excitation force acting on the raft and the wave power capture factor of the power take-off (PTO) system. Taking the maximum wave energy capture factor as the optimization objective, the optimal geometric parameters of the bionic raft are calculated and determined by numerical simulation. Subsequently, the effects of wave period, raft draught, and the linear viscous damping coefficient of the PTO system on the wave excitation force, raft motion, and wave energy capture factor are investigated in the frequency domain. Furthermore, the dimensionless optimal values of the aforementioned influencing factors are presented and discussed as the wave energy capture factors of the WECs reach their maximum values. This work provides a new design idea for the development and optimization of multi-raft WECs.