基于船波相对运动的船艏砰击仿真方法

在分析船波相对运动表达式的基础上计算船艏典型剖面的船波相对运动，探讨船艏入水过程中的砰击问题，对比船体某剖面3种入水仿真模型计算所得的砰击载荷，讨论三维外形和航行速度对船艏剖面砰击外载荷的影响。在该分析中，船体在规则波浪中的运动用基于三维势流理论的水动力软件AQWA计算获得，船波相对运动通过理论推导计算获得，用对船艏结构施加强迫运动的方式模拟船波相对运动的真实过程。采用An—sys／Ls—Dyna软件的流固耦合分析进行入水仿真，流体划分为ALE体积网格，船艏视为刚体，划分为Lagrange有限元网格。对比结果表明：在三维模型中，相邻剖面引起剖面最大压力点处的液面变化对该点的砰击压力有增大效果，航速有增大剖面砰击压力的作用，减小船艏底部纵向斜升角有利于降低砰击压力。

Simulation Method for the Slamming Problems of Ship Bows Based on the Relative Motion Between Hulls and Wave Surfaces

In this paper, the relative motion between ship＇s water plane and wave surface is discussed, where the calculation formulas are obtained, and a corresponding example is presented. Particularly, the slamming process of the ship bow into water is investigated ： the slamming pressure on the section is calcu- lated using three different methods, through which the relation between the peak pressure and the 3D shape and navigation speed is studied. Meanwhile, the ship motion in waves is simulated via AQWA, a hy- drodynamic software based on 3D-Potential Flow Theory, and the bow slamming simulation is realized by using the Fluid-Structure Interaction （FSI） algorithm in Ansys/Ls-Dyna （note that the motion of the ship bow is specified in advance in order to accomplish the simulation process）. In this slamming simulation, the fluid is modeled with ALE volume meshes, and the structures are modeled with Lagrangian finite ele- ments. The result shows that the change in the liquid level at a specific point, caused by the entry of adja- cent profiles, could increase the slamming pressure. Navigation speed also contributes significantly to the rising of slamming pressure. On the contrary, a small longitudinal deadrise angle at the bottom of the bow may help reduce slamming pressure.