Numerical Study on Coupling Effects of FPSO Ship Motion and LNG Tank Sloshing in Low-Filling Conditions
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摘要: 应用数值模拟方法对FPSO船舶运动与LNG液舱晃荡耦合问题进行了研究.这种全耦合问题的研究基于开源平台OpenFOAM开发的船舶与海洋工程水动力CFD求解器——naoe-FOAM-SJTU进行计算.液舱内部流场与外部流场同时求解.采用带有两个LNG液舱的FPSO船作为对象进行数值模拟,船舶放开3个自由度运动,并在90°浪向的规则波中进行模拟.液舱充水率为20%~20%,低于船外自由水面高度.这种低充水率的液舱会大大减少船舶的横摇运动,并且舱内的流体情况较为复杂.考虑了4种不同的入射波频率下船舶的运动,与实验结果进行了对比.数值模拟结果与实验结果对比吻合良好,验证了数值求解方法的可靠性.还对大波高情况下带有低充水率LNG液舱的船舶运动进行了数值模拟分析.在船舶运动与液舱晃荡全耦合情况下,观察到了液舱内流体的剧烈晃荡和舱壁的脉冲压力.
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关键词:
- LNG 液舱晃荡 /
- 耦合运动 /
- 低充水率 /
- naoe-FOAM-STJU求解器
Abstract: In this paper, numerical simulations of FPSO ship motion coupled with LNG tank sloshing with low-filling ratios are conducted. The fully coupled problem is addressed with our own unsteady RANS solver: naoe-FOAM-SJTU developed based on the open source tool libraries of OpenFOAM. The internal tank sloshing and external wave flow are solved simultaneously. The FPSO model includes 2 LNG tanks. For the ship 3-DOFs are released in the regular beam waves. The filling ratios of the 2 tanks are 20%~20%, lower than the external free surface. This kind of low-filling condition reduces ship roll motion significantly, and produces complex free surface shapes in tanks. 4 different incident wave frequencies are considered in the simulation in comparison with the existing experimental data. The comparison shows that the numerical results are in good agreement with the experimental data, proving the reliability of the proposed method. The filling conditions with large wave amplitudes are studied further, and due to the coupling effect, violent sloshing occurs in tanks and impulsive pressure forms on bulkhead.-
Key words:
- LNG sloshing /
- coupled motion /
- low-filling condition /
- naoe-FOAM-SJTU solver
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