船-桥梁浮式钢套箱碰撞数值模拟中的流场处理方法对比研究

本文采用Ansys/Ls-dyna对1000吨级船舶与浮式桥梁钢套箱的碰撞过程进行了数值仿真，为了较精确地分析流场处理方法对于数值计算结果的影响，分别采用了流固耦合方法和附加质量系数法来模拟碰撞过程中流场的作用，并对比分析了两种方法下浮式钢套箱的碰撞力、撞深、竖向位移、内能变化等计算结果。研究结果表明，与采用附加质量系数法的结果相比，考虑流固耦合时防撞钢套箱的最大撞深较小而最大撞击力较大，且随着碰撞能量的增加，最大撞击力明显大于采用附加质量系数法的结果。因此对于桥梁的防撞钢套箱设计，常规附加质量系数法偏于危险，有必要用流固耦合方法来考虑流场的作用。另外，船体的撞击能量越大时，浮式钢套箱的竖向位移约束也越重要，可以通过设计浮式钢套箱的压载水，减小钢套箱在碰撞过程中的竖向位移，以提高其吸能效果。

Comparative Study on Fluid Field Simulation Method for Numerical Simulation of Collision between Ship and Floating Anti-collision Steel Box

A numerical simulation of collision between a 1000t ship and a floating anti-collision steel box of bridge is carried out using Ansys/Ls-dyna. In order to figure out the influence of the flow field on the results of the numerical simulation, fluid-structure coupling method and the added mass coefficient method is applied respectively to account the effect of the flow field during collision process and the results from the two methods are compared, such as collision force, collision depth, vertical displacement and internal energy change of the anti-collision steel box. Results show that, while considering fluid-structure interaction, the maximum collision depth is smaller, meanwhile the maximum collision force is larger, and the maximum collision force is significantly larger with the collision energy increasing, compared to the added mass coefficient method. Therefore, considering fluid-structure interaction to account the effect of the flow field is necessary for the anti-collision steel box design of bridge. Furthermore, from results, the larger ship collision energy is, the more important vertical displacement is. By designing the ballast water capacity appropriately, the vertical displacement of steel box during collision process can be reduced and the energy-absorbing capability can be improved.