Abstract: The water-entry of rotor-type "soft" cross-medium vehicle faces challenges of high impact loads and attitude instability. This paper conducts a systematic study on the wave-entry problem of the proposed rotor-type soft cross-medium vehicle, aiming to reveal its water-entry characteristics and dynamic response mechanisms. First, a numerical model of fluid-structure interaction with multiple degrees of freedom is developed based on hydrodynamics and rigid-body dynamics, with experimental validation confirming the reliability of the numerical approach. Subsequently, this numerical method was employed to quantitatively investigate the entry loads and motion stability under various wave parameters and entry timings. It is found that a higher entry height of the vehicle increases the slamming load, but it reduces the disturbance caused by waves. Long waves can distribute the local impact force and reduce pressure concentration. When the vehicle enters along the waves at its phase, the generated dissipates kinetic energy along its tail effectively reduces the load amplitude. These findings provide support for the optimization of the entry strategy. The wave crest phase should be adopted as the extreme design condition, and the wave node entry can serve as a low-impact water-entry solution.

Key words: soft trans-medium, submersible-aerial vehicle, numerical simulation, wave environment, water entry characteristics