Fixed and Control Motion Response of a Surface-Piercing Hydrofoil in Multiphase Flow and in Waves

The objective of this work is to investigate the hydrodynamic and hydroelastic response of a surface-piercing hydrofoil at fixed attitudes and during controlled motions in multiphase flow and waves. Experiments were conducted in the depressurized wave basin (DWB) at the Maritime Institute in the Netherlands (MARIN). Results show that waves tended to accelerate the transition from fully wetted (FW) to fully ventilated (FV) flow. The transition to FV flow also occurs earlier at smaller cavitation numbers. Controlled yaw oscillations did not influence the mean load coefficients in FW or FV flows. However,even very slow periodic yaw oscillations significantly delayed both transition to FV flow and recovery to FW flow from partially cavitating (PC) and FV flows, dramatically increasing the hysteresis in the hydrofoil’s lift. Sinusoidal heave oscillations did not have a significant impact on the slow moving time-averaged performance compared to fixed draft cases; however, heave oscillations did affect the cavitating and ventilating inception condition and the resulting hysteresis response. The load change due to transition between FW and FV flow during heave oscillation was found to be very significant and very sudden. Sinuisoidal sway motion led to oscillations in the effective angle of attack (α_e), which in turn produced like oscillations in both loads and deformations. The degree of change depends on the sway amplitude and sway rate. Sway oscillations tended to delay transition to FV flow compared to cases with a fixed angle of attack; however, sway motions accelerated transition from PC to FV flow in depressurized conditions. Finally, roll oscillations led to small oscillations in heave and α_e, which led to oscillations in loads and deformations. The presence of a sufficiently large vaporous PC will significantly accelerate transition to ventilation in waves, particularly for cases with large roll motions.