Analytical study on hydrodynamic performance of a raft-type wave power device

In this paper, an analytical model is developed for the motion response and wave attenuation of a raft-type wave power device. The analytical solution of diffraction and radiation problem of multiple two-dimensional rectangular bodies floating on a layer of water of finite depth is obtained using a linearized potential flow theory. Wave excitation forces, added masses and wave damping coefficients for these bodies are calculated from incident, diffracted and radiated potentials. Upon solving the motion equation, response, power absorption and wave attenuation of a raft-type wave power device are obtained. The model is validated by comparison of the present results with the existing ones, and energy conservation is checked. The validated model is then utilized to examine the effect of power take-off damping coefficient, raft draft, spacing between two rafts, water depth, and raft numbers on power absorption and wave transmission coefficient of raft-type wave power device. The influence of structure length ratio is also discussed. It is found that the same wave transmission coefficient can be obtained by any certain raft-type wave power device, regardless of wave propagation direction.