Wave propulsion and sea-keeping enhancement for ships in rough sea condition by flapping foils

When sailing in rough seas, ships are subject to wave excitation forces that increase drag, damage the hull structure, affect equipment operation, and even result in ship accidents. By extracting wave energy for the ship in rough seas, the ship's safety can be improved and its energy consumption is reduced. In this paper, the flapping foils are arranged in tandem on both sides of the ship and are subjected to water pressure and shear forces, which passively change the angle of attack and produce force to propel the ship. The foils can be deployed in rough seas to stabilize the ship and retracted in calm water. The ship's motions with foils are modeled and the influence of flapping foils on ship stability is investigated in the frequency domain, which reveals that foils improve ship stability. Numerical studies in STAR-CCM + show that the foils may extract wave energy to propel the ship and generate an anti-pitching moment under different wave encounter angles and different ship speeds.