Numerical Investigation of Multistage Water-Entry Hydrodynamics of a Light Seaplane Float Under Regular Waves

Under wave conditions, water entry of a seaplane float involves rapid migration of the contact region, transient pressure development, load variations, and float pitching motion. A three-dimensional single-float rigid-body surrogate model of a light amphibious aircraft was developed, with surge, heave, and pitch motions considered within the dynamic fluid–body interaction (DFBI) framework. Within this framework, the effects of horizontal velocity, vertical velocity, wave height, and wavelength on slamming load, drag, pitch response, bottom-pressure distribution, and free-surface evolution were investigated. Within the investigated conditions, increasing the initial horizontal velocity from 4 to 10 m/s reduced the initial-contact peak from about 36.2 to 23.3 kN, while increasing the subsequent-impact peak from 37.65 to 54.56 kN, shifting the dominant loading toward the later stage. Increasing the initial vertical velocity produced the opposite redistribution: the initial-contact response was progressively strengthened, whereas the subsequent impact weakened, causing the dominant loading to shift toward the early stage. Wave height mainly altered the timing of float–wave contact and the distribution of loading between successive impacts, resulting in a non-monotonic variation in the maximum slamming load over the investigated range of 0.1–0.7 m. For wavelengths of 5–9 m, the pressurized region beneath the float became broader and more spatially coherent as wavelength increased, accompanied by an overall increase in the maximum slamming load.