船舶运动与液舱晃荡耦合频域计算方法

Simulation of ship motions coupled with tank sloshing in frequency domain

    摘要
  • 摘要:
      目的  随着载液船舶(LNG，FPSO，FLNG等)的大型化以及对作业效率和作业安全性要求的不断提高，液舱晃荡以及由其引起的船舶运动问题愈发严重。为有效解决该问题，
      方法  首先，基于三维势流理论和波浪辐射绕射理论，采用高阶边界元法开发波浪与三维结构物作用的计算程序，选取某艘FPSO船型，将本程序的计算结果与采用水动力计算软件AQWA，HYDROSTAR所得结果进行对比，验证程序的准确性；然后，将液舱晃荡水动力系数的频域求解方法与船舶运动的频域求解方法相结合，建立考虑液舱晃荡影响的船舶频域运动方程，获得耦合液舱晃荡后的船舶运动响应；最后，以一艘加载了2个液舱的FPSO船型为例，论证该计算方法的准确性。
      结果  通过对比液舱不同装载下的船舶运动响应，发现存在着船舶的横摇共振频率出现偏移、耦合横摇运动幅值存在多个峰值，以及液舱装载不同对船舶运动的影响也不同等现象。
      结论  所做研究可为载液船舶运动响应设计提供参考。

     

    Abstract:
      Objectives  With the increase in the size of the ship with liquid tanks (LNG, FPSO, FLNG, etc.) and the improvement of work efficiency and operational safety, the coupled problem between the tank sloshing and the resulting ship motions have become more serious.Therefore, to effectively solve it,
      Methods  firstly, based on 3D potential flow theory and wave radiation/diffraction theory, the simulation program using the higher-order Boundary Element Method(BEM) which can compute the load and motion of 3D floating structures induced by wave is developed.To verify the accuracy of this simulation program, the simulation results of a FPSO model is compared with the results obtained from the hydrodynamic software HYDROSTAR and AQWA.Secondly, a equation for the ship motions in frequency domain considering the effects of the tank sloshing is established to obtain the coupled motion response by combining the frequency domain solution method for the hydrodynamic coefficient of the tank sloshing with that for the ship motion.Finally, a FPSO ship with two liquid tanks is taken as an example to demonstrate the accuracy of this simulation program.
      Results  By comparing the motion responses of the ship with different tank filling levels, it is found that there is a shift in the roll resonance frequency, there are multiple peaks in the coupled roll motion, and different effects are caused due to different tank filling levels.
      Conclusions  This study provide a reference for the motion response design of the ship with liquid tanks.

     

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