不同姿态下救生艇高空自由下落的动力学特性

Dynamic Characteristics of Lifeboat’s Free-fall from High Altitude under Different Postures

救生艇从高空自由下落到水面上的过程是典型的结构物入水问题。以一艘刚性充气艇为计算模型,基于动态重叠网格法对该艇在某高度处以不同姿态自由下落的过程进行数值模拟,得出其在下落过程中的垂向速度、加速度和下落距离等物理量的变化情况。对比分析结果表明:初始下落姿态决定着救生艇入水后的运动状态,横倾在艇宽方向上的运动比较剧烈,艏倾和艉倾在艇长方向上的运动比较剧烈;救生艇艏倾入水时的埋艏现象和甲板上浪现象比较严重;通过调整艇体下落时的初始姿态,可改变其入水角度,有效减缓甲板上浪。

The process of a lifeboat falling freely into the water from high altitudes is a typical issue of structure-entering-water. A rigid inflatable boat is taken as the calculation model and the dynamic overset grid method is used to perform the numerical simulation of the free-fall process of the boat from a certain height under different postures, to obtain the variation of physical values of vertical velocity, acceleration, falling distance and etc. The result shows that the initial falling posture determines the motion states of the lifeboat after entering the water. Heeling is severe in the transversal direction, trimming by bow or stern is more severe in the longitudinal direction, while the buried bow and green water on deck is more serious when the bow is tilted into the water. Adjusting the initial posture of the boat during its fall is possible to change the angle of boat entering water and effectively reduce green water on deck.