Numerical simulation analysis of the stability of lifeboats during release under high sea conditions

As the main water rescue vehicle, lifeboats are an important guarantee for the safety of crew and passengers. During the release of the survival crafts affected by extreme conditions, such as mother ship shaking and strong winds, the survival crafts will move violently in multiple degrees of freedom directions, which may cause collision or the failure of the lifeboat launching devices. As a result, it will lead to the rescue efficiency reduction and crew casualties. In this paper, the 3D model of lifeboat system was established by SolidWorks firstly. Based on equation of the Lagrange, the dynamic simulation software ADAMS/View was used to model and analyze the relationship between the hull roll, pitch, wind load and the release length of the davit cable and the response of the lifeboat, that is, the amplitude and frequency of its swing. The simulation results show that the ship's rolling and pitching exert the most significant effect on the lifeboat's release process, and the wind load generally does not cause the lifeboat's dangerous swing. Lifeboat swings weaker and weaker as it gets closer to the sea. Therefore, the design of the controller to actively control the expansion of the boom and the release speed of the boat winch is helpful to realize collision avoidance and shimmy reduction and improve the safety of the lifeboat in the release process. The research results can provide theoretical basis and guidance for the design and operation of the release mechanism of various types of lifeboats.