Maximising Pitch Energies of a Wave-Propelled ASV to Increase Forward Speed

Pitch-driven, wave-propelled vessels are able to use the energy contained solely within the waves to propel themselves across theoretically unlimited distances. For this type of platform, maximising the energy harnessed from the environment and transferred to the vessel's pitch motions is important for increasing forward speed. In this paper, a parametric range of hullforms based on a Wigley hull is analysed in terms of the average energy-per-second in the pitch motions and the average energy lost to added resistance. This reveals that there exists a range of hullforms where the energy in the pitch motions can be 1.6 times greater than the energy lost to added resistance. The analysis is repeated over a range of vessel drafts, which reveals that a beam to draft ratio of less than 3 allows a hullform to be designed to achieve this effect. This work indicates that the hullform is a crucial part of the functioning of a wave-propelled vessel, and it can be designed to maximise energy harnessed from the waves. Provided this energy is effectively transferred to the foils, it can lead to an increase in forward speed.