Research On Sloshing Hydrodynamic Characteristic And Load Transfer For LNG Tank

Under the background of current green environment protection,the dual fuel power ship has been widely valued and developed rapidly in recent years.Among them,liquefied natural gas(LNG)storage technology and fuel tank scheme design are the key core technologies for clean and environmental protection high-quality natural gas energy.Among various types of LNG storage tanks,SPB fuel tank has a higher deck utilization ratio and a better application prospect.However,the sloshing phenomenon of LNG fuel inside the tank is also one of the key issues in the fuel tank design.In this paper,SPB fuel tank is taken as the research object,and the sloshing hydrodynamic characteristics of the internal liquid are studied by numerical simulation method,which provides theoretical basis for the form design of internal components of SPB fuel tank.On this basis,the method of LNG sloshing load extraction and application is studied,and the process of sloshing hydrodynamic load transfer based on workbench is further studied.The specific research contents are as follows:First of all,the algorithm and model of sloshing hydrodynamic analysis are established,and the convergence analysis and accuracy verification are completed.On this basis,the CFD numerical simulation and the empirical formula of classification society are compared and analyzed according to the conditions of low and medium loading liquid level and different internal swaying bulkhead structure,which provides the research basis for the subsequent analysis of natural frequency of LNG fuel tank.Secondly,according to the constantly changing LNG liquid level in the process of ship navigation,the numerical simulation analysis of different loading liquid level and different internal structure is carried out.The numerical results show that with the decrease of LNG level,the internal components have more and more influence on the overall moment of the tank,which needs to be considered in the structural design of the fuel tank.In addition,the number of bulkheads has little effect on the overall moment of sloshing,but has a greater effect on the structure of bulkheads.With the decrease of cabin loading height,the effect is more obvious,which can provide theoretical basis for bulkhead structure design.Then,according to the preliminary calculation results of sloshing based on the fuel tank model,and based on the theory of ship motion in waves and sloshing hydrodynamic analysis,two typical types of motion amplitude maximum and motion frequency equal to the natural frequency are formulated for subsequent analysis.On this basis,the sloshing model of typicalLNG fuel tank is established for five different loading conditions,and the sloshing hydrodynamic analysis and simulation are carried out.According to the results of numerical simulation,cfd-post and ANSYS APDL are used to transfer the fluid load to the structure.However,in the process of load data transmission,it is found that the current method to extract and apply the sloshing pressure of the structure at all times is very complex and cumbersome.Finally,in order to solve the above problems,it is more convenient to transfer sloshing hydrodynamic load for SPB LNG fuel tank structure design,and to explore the sloshing hydrodynamic load transfer process based on workbench.Firstly,the workflow of workbench analysis is established,and the hydrodynamic calculation is completed by UDF compilation through the initial model and grid.The results show that the CFD surface load can transfer the load accurately in the steady and transient conditions,and the current process can complete the load loading and structural calculation,so it also proves that the current process is feasible.Due to the large number of internal components in SPB cabin,it is proved that the load transfer will not be affected by adding internal components through model verification.On the one hand,the intersection line between the internal components and the outer panel of the cabin will not affect the load transfer;on the other hand,after the internal components are added,the CFD grid corresponds to two surfaces while the structure corresponds to a single surface,and this different corresponding way will not affect the load transfer,so the internal components will not affect the load transfer,which again proves that the workflow determined in this paper can be used for LNG cabin.The structure design provides sloshing hydrodynamic load,which will not affect the load transfer due to the existence of internal components.