﻿ 基于CFD的船舶破舱进水流量系数研究
 舰船科学技术  2019, Vol. 41 Issue (10): 59-62 PDF

CFD simulation of coefficient of discharge for damaged ship
ZHANG Si-hang, GU Jun, WU Jun, CHEN Zhe-chao
Marine Design and Research Institute of China, Shanghai 200011, China
Abstract: Flooding is one of the most concerned critical events while researching marine safety. In this paper, a series of simplified models based on bottom damaged ship has been established and Ansys Fluent has been used to perform simulation calculations by taking VOF method. The result of calculations offered the transient-based coefficient of discharge. By comparing the differences between coefficient of discharge with different sizes、shapes and depths of bottom breach, it can offer a useful reference for crew to evaluate ship damage and help quicker solving problem.
Key words: damaged ship     coefficient of discharge     Fluent     VOF method
0 引　言

1 理论基础 1.1 VOF方法

1）a=0：在该单元中目标流体不存在；

2）0<a<1：在该单元中有至少包括目标流体在内2种或以上流体类型存在，且该单元内存在不同流体间的交界面；

3）a=1：在该单元中充满了目标流体。

 $\frac{\rm{1}}{{{\rho }_{{q}}}}\left[ \frac{\partial }{{{\partial }_{t}}}\left( {{a}_{q}}{{\rho }_{q}} \right)+\nabla \left( {{a}_{q}}{{\rho }_{q}}\overset{\to }{\mathop{{{v}_{q}}}}\, \right)={{S}_{{{a}_{q}}}}+\sum\limits_{p=1}^{n}{\left( \overset{\bullet }{\mathop{{{m}_{pq}}}}\,–\overset{\bullet }{\mathop{{{m}_{qp}}}}\, \right)} \right]\text{。}$

1.2 控制方程

 $\frac{\partial u}{\partial x}+\frac{\partial v}{\partial y}+\frac{\partial w}{\partial z}=0\text{。}$

 $\rho \frac{{\rm d}v}{{\rm d}t}=\rho F-gradp+\mu {{\nabla }^{2}}v\text{。}$

1.3 进水流量系数

 ${{p}_{1}}\cdot\rho g{{z}_{1\cdot}}\frac{1}{2}\rho v_{1}^{2}\ll {{p}_{2}}\cdot pg{{z}_{2}}\cdot\frac{1}{2}\rho v_{2}^{2}\text{。}$

 \begin{align} BL=&First\_cell(1-growth\_rat{{e}^{\max imum\_layers)}})/\\ &(1-growth\_rate)\text{，} \end{align}

 ${{Q}_{ideal}}=A{{v}_{2}}\text{。}$

 图 1 破口进水情况（左）与进水流量系数示意（右） Fig. 1 Sketch for coefficient of discharge

 ${{C}_{d}}=\frac{{{Q}_{actual}}}{{{Q}_{ideal}}}\text{，}$

 ${{Q}_{actual}}={{C}_{d}}{{A}_{d}}\sqrt{2g({{h}_{1}}-{{h}_{2}})}\text{。}$

2 模型与计算参数 2.1 模型尺寸

 图 2 几何模型划分示例C1-300-3D Fig. 2 Model geometry example C1-300-3D

 图 3 几何模型不同破口示例S1-500-3D（左），T1-500-3D（右） Fig. 3 Model geometry example with different shapes of breach S1-500-3D（left）T1-500-3D（right）
2.2 网格划分

 图 4 C1-300-3D破口处网格（左）和柱体内水平面以下部分网格（右）示意 Fig. 4 Mesh example of C1-300-3D breach（left）and cylinder below water line（right）
2.3 计算参数

3 结果与分析 3.1 破口形状对进水流量系数的影响
 图 5 不同破口形状进水填充速率图 Fig. 5 Charge rate for different shapes of breach

 图 6 深度500 mm，1%破损，不同破口形状流量系数-时间曲线（前5 s） Fig. 6 Cd value-time curve for different shapes of breach with 500 mm depth and 1% damage（first 5 second）

3.2 破口尺寸对进水流量系数的影响
 图 7 深度300 mm，圆孔，不同破口尺寸流量系数-时间曲线（前5 s） Fig. 7 Cd value-time curve for different sizes of breach with 300 mm depth and circle shape（first 5 second）

 图 8 深度500 mm，圆孔，不同破口尺寸流量系数-时间曲线（前5 s） Fig. 8 Cd value-time curve for different sizes of breach with 500 mm depth and circle shape（first 5 second）

3.3 破口水深对进水流量系数的影响
 图 9 圆孔，1%柱底面积，300 mm和500 mm水深流量系数-时间曲线（前5 s） Fig. 9 Cd value-time curve for 300 mm and 500 mm depth with circle shape and 1% damage（first 5 second）

 图 10 圆孔，2%柱底面积，300 mm和500 mm水深流量系数-时间曲线（前5 s） Fig. 10 Cd value-time curve for 300 mm and 500 mm depth with circle shape and 2% damage（first 5 second）

 图 11 圆孔，4%柱底面积，300 mm和500 mm水深流量系数-时间曲线（前5 s） Fig. 11 Cd value-time curve for 300 mm and 500 mm depth with circle shape and 4% damage（first 5 second）

4 结　语

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