Simulation method and coupled response of bow skirt–ramp deployment in hovercraft

Objectives  To address the problems of low deployment efficiency and insufficient stability of the bow landing ramp of a hovercraft during landing operations under conditions such as restricted air exhaust, this study investigates the dynamic response characteristics of the airbag–ramp coupled system and explores effective methods to improve the reliable deployment capability of the ramp under abnormal operating conditions.

Methods Based on the explicit dynamic finite element method, a rigid–flexible–fluid coupled numerical model of the hovercraft bow skirt airbag–landing ramp system is established. The effects of different exhaust orifice areas on the airbag internal pressure, exhaust mass flow rate, and ramp motion response are systematically analyzed. For the exhaust failure condition, an equivalent mechanical transmission device is introduced to actively drive the ramp deployment by applying additional mechanical torque.

Results  Under normal exhaust conditions, the exhaust orifice area is the dominant parameter governing the airbag depressurization process and the dynamic behavior of ramp deployment. When the area of a single exhaust orifice increases from 0.1 m² to 0.45 m², the decay rate of the airbag internal pressure is significantly accelerated, and the time at which the ramp enters the gravity-dominated falling stage occurs earlier. Consequently, the deployment time is reduced from 11.3 s to 2.6 s. The peak angular velocity shows an upward trend with non-monotonic response characteristics, and a stable inverse correlation is observed between the exhaust orifice area and the ramp deployment time. By contrast, when the ramp mass increases from 6256 kg to 8181 kg, the deployment time is shortened by only 0.5 s, indicating a limited influence on the system response and a clear marginal effect. Under exhaust failure conditions, the application of additional mechanical torque can effectively shorten the deployment time and improve motion stability. When the prescribed angular velocity increases from 0.14 rad/s to 0.22 rad/s, the maximum additional mechanical torque required to maintain uniform deployment rises from 1.16×10⁶ N·m to 1.54×10⁶ N·m. The required torque increases in stages during the ramp falling process and exhibits a positive correlation with the angular velocity. The stress analysis of the airbag shows that the front folding region and the lateral bulging region are the primary areas where stress and deformation are concentrated.

Conclusions  By appropriately matching the airbag exhaust orifice parameters with the ramp structural parameters, and by supplementing the system with mechanical transmission devices under abnormal operating conditions, the reliability and operational efficiency of hovercraft landing ramp deployment can be significantly improved.