Experimental and Numerical Study of an Oscillating Foil Near the Free Surface

Abstract This work presents experimental and numerical results to study the performances of an actively pitching and heaving NACA0015 hydrofoil near the free surface, as a biomimetic propulsion system for ships. The experiments are carried out in the IFREMER current and wave tank at Boulogne-sur-Mer for several heave and pitch amplitudes. The influence of the phase lag between the pitch and heave motions is also investigated, as well as the hydrofoil performances in regular waves. The experiments consists of forces measurements and they are compared with numerical predictions of the hydrodynamic forces using the potential flow code PUFFIn in its latest unsteady version. Comparisons with Reynolds Averaged Navier-Stokes (RANS) calculations are presented for cases where the discrepancies between the potential code and experimental results are significant. Overall, the mean numerical forces exhibit similar trends to the experimental averages, validating the use of the potential flow code to optimize foil kinematics and design in ship propulsion applications. Keywords Oscillating Foil; Free Surface; Regular Waves; Experimental Fluid Dynamics; Boundary Elements Method; Reynolds Averaged Navier Stokes