  An investigation of the influence of the hydrofoil on load reduction
performance during an amphibious aircraft landing on still and wavy water is
conducted by solving the Unsteady Reynolds-Averaged Navier-Stokes equations
coupled with the standard $k-\omega$ turbulence model in this paper. During the
simulations, the numerical wave tank is realized by using the velocity-inlet
boundary wave maker coupled with damping wave elimination technique on the
outlet, while the volume of fluid model is employed to track the water-air
interface. Subsequently, the effects of geometric parameters of hydrofoil have
been first discussed on still water, which indicates the primary factor
influencing the load reduction is the static load coefficient of hydrofoil.
Furthermore, the effects of descent velocity, wave length and wave height on
load reduction are comprehensively investigated. The results show that the
vertical load reduces more than 55$\%$ at the early stage of landing on the
still water through assembling the hydrofoil for different descent velocity
cases. Meanwhile, for the amphibious aircraft with high forward velocity, the
bottom of the fuselage will come into close contact with the first wave when
landing on crest position, and then the forebody will impact the next wave
surface with extreme force. In this circumstance, the load reduction rate
decreases to around 30$\%$, which will entail a further decline with the
increase of wave length or wave height.
