Re-entrant honeycomb impact mitigation during oblique water entry in waves

Water-entry impact in wave environments is a complex fluid–structure interaction problem involving transient hydrodynamic loading, structural deformation, and attitude variation. Variations in the free-surface profile and local impact conditions induced by waves can substantially alter the impact loads and dynamic response of the entering body. In this study, the water-entry response of a cylinder equipped with an embedded re-entrant honeycomb structure is investigated under prescribed wave conditions using a validated fluid–structure interaction framework. The effects of wave phase, steepness, impact velocity and angle, and structural parameters including lattice geometry, rotational orientation, and nose geometry are systematically explored. The results indicate that wave phase, impact velocity, and impact angle appreciably influence the transient impact response, whereas wave steepness has a comparatively limited effect within the investigated range. The embedded lattice effectively reduces the peak acceleration by inducing a plateau-like response through progressive compression and buckling. By correlating the transient acceleration response with the evolution of lattice compression and deformation, the coupled mechanism involving hydrodynamic loading, progressive structural collapse, and impact energy absorption is elucidated. A favorable stiffness range is identified among the investigated configurations: insufficient stiffness leads to stroke-limited collapse and secondary impact, whereas excessive stiffness limits structural deformation and reduces mitigation effectiveness. Rotational orientation has a limited influence on global loads but affects attitude stability, whereas nose geometry governs baseline impact severity and structural engagement. These findings reveal the coupled relationship between wave-dependent hydrodynamic loading and internal lattice deformation, providing new insights into the design of internally integrated energy-absorbing structures for water-entry systems operating in realistic wave environments.