Dynamics of wave powered boat considering the heave and pitch motion excited by waves

Wave-powered boats generate forward propulsion by utilizing the heave and pitch motions induced by waves, allowing for potentially unlimited endurance. In this paper, the propulsion and energy utilization performance of tandem hydrofoils mounted on a wave-powered boat considering the coupled heave and pitch excitation is investigated based on a fluid and multibody coupling method. The coupled motion of the tandem hydrofoils is mathematically described, and the propulsion effects of the front and rear hydrofoils, as well as the pressure distribution and the vortex interaction, are examined under the pure heave, pure pitch and coupled heave and pitch excitations. The research indicates that the interplay between heave and pitch motion is critical for maximizing the tandem hydrofoil's propulsion performance, and the pitch motion is the key component responsible for enhancing the energy conversion efficiency of the hydrofoils. The pitch amplitude in coupled excitation affects the phase difference between the movements of the tandem hydrofoils, resulting in an asymmetric thrust and resistance distribution during their upstroke and downstroke, which has the potential to affect the stability of the tandem hydrofoils. Furthermore, an increase in pitch amplitude can reduce the interference of the front hydrofoil's wake on the rear hydrofoil, significantly enhancing both the propulsion performance and energy efficiency of tandem hydrofoils. This study can provide a reference for the design and optimization of the propulsion performance of the wave-powered boats.