Propulsion of an active flapping foil in heading waves of deep water

The propulsion of a flapping foil in heading waves has been investigated through the velocity potential theory. The trajectory of the flapping foil is prescribed with the combined sinusoidal heave and pitch motions. Boundary element method is introduced to solve the boundary value problem and a time stepping scheme is adopted to simulate the interaction of the foil and Stokes waves of infinite water-depth. The nonlinear free surface boundary conditions are imposed when updating the free surface. The effects of the frequency difference between foil motion and waves have been investigated. When the encountered wave frequency equals the flapping frequency, hydrodynamic performance of the flapping foil can be enhanced significantly.