Flow over a hydrofoil at incidence immersed within the wake of a propeller

The flow over a hydrofoil in the wake of a marine propeller is studied using large-eddy simulation on a cylindrical grid composed of 3.8 billion points. Four angles of incidence of the downstream hydrofoil are considered, ranging from 0 ° to 15 °. The impact of the propeller wake on the flow within the boundary layer of the hydrofoil is substantial, increasing the skin-friction and producing significant spanwise flows, associated especially with the deflection of the tip and hub vortices. This deflection is strongly influenced by the incidence angle of the hydrofoil, producing an overall expansion of the propeller wake on its pressure side and a contraction on its suction side. The tip and hub vortices are also the major source of pressure fluctuations on the surface of the hydrofoil, affecting this way its unsteady lift and drag coefficients. On the pressure side, the most significant pressure fluctuations are due to the hub vortex, while on the suction side, their maxima originate from the overlapping effects by the tip vortices and the adverse streamwise pressure gradient, promoting the instability of the boundary layer. Pressure fluctuations are an increasing function of the incidence of the hydrofoil on both its pressure and suction sides.