A New Aspect of the Ground Effect: The Two-way Interactions between an Airplane Flying in the Vicinity of Sea Water and the Free Surface Waves

This study presents intensive numerical simulations of a general aviation airplane flying near a wavy water surface, considering the effects of ground proximity and wave amplitude on aerodynamic forces and moments. The Stokes third-order wave model was employed, and numerical results were validated using limited wind tunnel tests on a ۳D-printed model, as well as existing NACA ۴۴۱۲ near-ground experimental data. Simulations for both flat and wavy surfaces reveal that above an elevation of h/c=۱.۵, aerodynamic coefficients remain similar to those near a flat surface. However, at lower clearances, aerodynamic responses exhibit strong oscillatory behavior, potentially leading to resonance and instability. The oscillations in lift (CL​) and drag (CD​) closely follow wave shape, while the pitching moment coefficient (Cm​) shows a distinct phase lag. Large-amplitude waves significantly impact stability, leading to severe pitch oscillations, which may pose risks for aircraft flying near stormy sea surfaces. Contrary to the typically beneficial ground effect for wing-in-ground (WIG) aircraft, this study highlights the destabilizing influence of large surface waves in near-ground flight.

کلیدواژه ها:

Ground effect ، Downwash ، Wavy water ، Induced velocity ، Venturi