Wave energy scavenging performance of heaving and pitching ship bow foils

Bow foils have the potential to significantly improve the efficiency of marine craft. Conventionally, ship bow foils act as an energy saving device, directly converting wave energy to hydrodynamic forces, reducing the added resistance in waves and generating an additional ship thrust. In this paper, experimental results from a novel, bow foil arrangement that is free to heave relative to the ship are presented and described, as a means to generate electrical power directly. The experimental results, which demonstrate a new mode of operation for bow foils, compares the ship performance with and without the foil, on a free running 2 m bulk carrier model, over a range of wave frequencies, in regular head waves with a constant forward speed. The effect on ship motions, delivered power and the generated power, efficiency, Strouhal number and capture width ratios are presented. The results show experimentally that power can be recovered and that the system acts to reduce the pitch motion, with negligible influence on the heave motion. The concept represents a new mode of operation for bow foils and an approach for marine craft to effectively act as wave energy converters for improved efficiency and capability, with potential applications to a variety of ships that loiter e.g., patrol vessels, offshore supply vessels, wind farm crew transfer vessels and autonomous surface vehicles.