Unsteady flow around a hydrofoil beneath waves

A general model for studying the unsteady free surface flow generated by a hydrofoil moving beneath a wavy free sur- face is presented. The flow field is assumed irrotational ev- erywhere except for a thin wake shed from the trailing edge. A boundary integral formulation for the velocity field is in- troduced and integral equations for the unknown velocity components are solved by an accurate as well as efficient method. The solution is stepped forward in time by evolu- tion equations for the free surface and the wake. Test cases are solved for which experimental results are available. Both foils with and without angle of attack are considered and experimental wave profiles are successfully recovered. Drag and pressure coefficients on the hydro- foil satisfactorily compare with the experiments. The abil- ity to handle highly nonlinear behaviours of the free surface is shown by computing breaking waves generated by a foil slightly immersed with a large angle of attack.