﻿ 基于CFD的船舶破舱进水时域模拟
 舰船科学技术  2017, Vol. 39 Issue (10): 29-33 PDF

Time-domain simulation of the flooding of a damaged roro ship based on CFD
ZHENG Yu, MA Ning, GU Xie-chong
State Key Laboratory of Ocean Engineering, Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiaotong University, Shanghai 200240, China
Abstract: Damage and flooding of ships will lead to danger even capsizing so that is a important problem of ship safety research. Ship may reach a more dangerous situation in mid flooding progress than final condition. In this paper, we used STAR-CCM+ as research tool to achieved the time-domain simulation of the triansient asymmetry flooding progress of a RoRo ship.Direct at free-floating damaged RoRo ship, we used VOF method to simulate the water-air free surface, and firstly used the Overset Grid dynamic mesh method with DFBI six degree of freedom solver to deal with the ship motion like heaving and rolling in ship damage and flooing problem. In the simulation result, we can get the the liquid level in compartment and ship floating conditions over time, and observe transient phenomenons like jet flow and splashing. The final floating condition result agreed well with the traditional quasi-static method result.
Key words: damage     flooding     time-domain simulation     overset
0 引　言

Spouge[1]对于European Gateway客滚船的倾覆进行了分析探讨，首次提出了“对称舱室的瞬时非对称进水”。Santos and Guedes[2]应用了6自由度时域模拟了滚装船的瞬时进水过程，在进水舱室中用大的流动障碍物模拟瞬时不对称进水，整个过程假定液面水平。Zhiliang Gao等[3]用一种N-S方程求解器结合VOF方法模拟了固定状态下客滚船进水，并用该方法测试了二维和三维的溃坝模拟问题。李佳[4]采用伯努利方程的准静态法求解了自由漂浮状态下不考虑外流体域的船舶进水过程。曹雪雁[5]采用SPH法对于三维船舶破舱进水特性进行了模拟研究。刘强[6]基于Fluent平台局部网格重构动网格技术和用户自定义函数（UDF）进行了对进水以及二维舱室耦合运动的模拟，并探讨了空气压缩性对于进水过程的影响。上述方法均未对三维实船对象在自由漂浮状态下的破舱流动特性、船体与水的横摇耦合运动进行时域模拟研究。

1 数值模拟的理论基础 1.1 控制方程

 $\frac{{\partial u}}{{\partial x}} + \frac{{\partial v}}{{\partial y}} + \frac{{\partial w}}{{\partial z}}{\rm{ = }}0{\text{，}}$ (1)

 $\rho \frac{{d\nu }}{{dt}} = \rho F - gradp + \mu {\nabla ^{\rm{2}}}v{\text{，}}$ (2)

 $\begin{split}&\int_V \!\! {\frac{\partial }{{\partial t}}\left( {\rho \phi } \right){\rm{d}}v + } \!\! \int_V {div\left( {\rho v\phi } \right){\rm{d}}}v =\\&\;\;\;\;\;\;\;\;\;\;\;\;\;\;\int_V {div\left( {\Gamma grad\phi } \right){\rm{d}}v + } \!\! \int_V {S{\rm{d}}v} {\text{。}}\end{split}$ (3)

1.2 VOF方法

VOF（Volume of fluid）方法的基本原理是通过研究网格单元中流体和网格体积比函数F来确定自由面，追踪流体的变化，而非追踪自由液面上质点的运动。VOF方法可以处理自由面重入等强非线性现象，所需计算时间短、存储量少。

 图 1 VOF方法[7] Fig. 1 Volume of fluid method[7]
1.3 重叠网格（Overset Grid）动网格处理技术

Overset grid技术[89]是将复杂的流动区域分成几个几何边界较为简单的子区域，各个子区域之间的计算网格独立生成，彼此存在重叠或覆盖关系。流场信息通过插值在重叠区域的边界上进行交换和匹配。

2 计算模型尺寸

 图 2 完整船体几何模型 Fig. 2 Geometry model of intact ship

 图 3 破损舱室 Fig. 3 Damaged compartment

 图 4 破口 Fig. 4 Opennig
3 网格划分与计算参数设定 3.1 网格划分

 图 5 整个计算域的网格配置概览 Fig. 5 Sketch of mesh arrangement in the whole computational domain

 图 6 重叠网格区域内部网格 Fig. 6 Mesh in overset region

 图 7 破口处网格细节 Fig. 7 Detail of mesh around opening

 图 8 初始状态插值区域 Fig. 8 Interpolation region of initial condition
3.2 计算参数

4 模拟计算与结果分析 4.1 计算结果

 图 9 各时刻自由液面示意图 Fig. 9 Sketch of free surface of different time

 图 10 船舶横倾力矩时历曲线 Fig. 10 Rolling moment curve

 图 11 船舶横倾角时历曲线 Fig. 11 Rolling angle curve
4.2 结果与准静态计算结果的比较分析

NAPA软件稳性模块的计算精度得到了各大船级社和设计公司的肯定，将其作为验证工具，结果可信。NAPA计算船舶浮态的方法是假定舱内液面均为水平的准静态方法。由NAPA稳性模块计算得到此客滚船在R6.2单舱室破损情况下最终船舶横倾角为3.4°，吃水增加0.039 m。

5 结　语

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