﻿ 基于OpenFOAM的液舱在波浪中运动特性研究
 舰船科学技术  2022, Vol. 44 Issue (1): 12-16    DOI: 10.3404/j.issn.1672-7649.2022.01.003 PDF

Motion characteristics of liquid tank in waves based on OpenFOAM
WANG Meng, CHEN Lin-feng, SUN Shi-yan
School of Naval Architecture and Dcean Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
Abstract: When the tank is filled with liquid and ice respectively, each particle of fluid has a different acceleration, but they are all the same for the ice, which will lead to the motion characteristics of inner liquid is quite different from that of the ice. In this paper, the process of two-dimensional liquid tank and ice tank pitching in waves will be simulated based on the open source software OpenFOAM. The comparison between air and water is made, to investigate the influence of inner liquid on the motion of the tank. The numerical model is established based on the N-S equation and the continuity equation, the finite volume method (FVM) is used to discretize the control equations, the fluid volume method (VOF) to capture the free surface, and the dynamic mesh technology to deal with the mesh deformation caused by the moving of body. The mutual dependence between inner liquid or ice, waves and the tank are investigated. It is found that the natural frequencies of water and ice are much different, their differences from wave frequency also get changed, which will further affect the motion amplitude of water tank and ice tank.
Key words: liquid tank sloshing     laminar flow     coupled motion     OpenFOAM     nonlinear
0 引　言

1 数学模型

 图 1 液舱计算域 Fig. 1 Computational domain of tank

 图 2 数学模型及坐标定义 Fig. 2 Mathematical model and coordinate system

 $\nabla \cdot {{\boldsymbol{U}}} = 0 ，$ (1)
 $\frac{{{\rm{D}}{\boldsymbol{U}}}}{{{\rm{D}}t}} = {{{F}}_b} - \frac{1}{\rho }\nabla p + \nu {\nabla ^2}{U}。$ (2)

 图 3 网格示意图 Fig. 3 Grid diagram
2 数值算例 2.1 收敛性分析

 图 4 网格收敛性分析 Fig. 4 Grid convergence analysi

 图 5 液舱自由晃荡纵摇角随时间变化曲线 Fig. 5 Pitch angle of the tank varying with time at free sloshing
2.2 结果分析

2.2.1 波高为0.2 m时水舱和冰舱运动时历对比分析

 图 6 当波高为0.2 m时不同波长下船舱纵摇角度随时间变化曲线 Fig. 6 The time history of pitch angle with different wavelengths at wave height is 0.2 m
2.2.2 波高为0.6 m时水舱和冰舱运动时历对比分析

 图 7 当波高为0.6 m时不同波长下船舱纵摇角度随时间变化曲线 Fig. 7 The time history of pitch angle with different wavelengths at wave height is 0.6 m
2.2.3 液舱内水的晃荡特性分析

 图 8 液舱内水晃荡随时间变化曲线 Fig. 8 The times history of inner liquid sloshing
3 结　语

1）相同形状和相同密度水舱固有周期大于冰舱固有周期，这是由于冰块相当于是刚体，每个质点的加速度都是相同的，而对于水，每个质点的加速度都不相同，这使得水舱即难加速度也难减速，最终导致水舱的固有周期大于冰舱。

2）受船舱固有周期与波浪周期相对关系的影响，在本文算例中，当波长逐步增加时，载冰舱运动幅值逐渐减小，而载水舱幅值逐渐增大，其深层次的原因是，船舱固有频率和波浪频率接近时，船舱将发生共振，此时运动幅值最大。

3）当波高不大时，液舱内流体随波浪柔和振荡，随着波高的增加，非线性效应逐渐显现，液舱内流体的高频振动特征也随之出现，在一个波浪周期内，流体质点可能出现双峰或三峰振动特征。

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