The Numerical Simulation And Experimental Research On Sloshing Of LNG Independent Type C Tank

Recently,as clean energy,LNG is brought into focus of globe world,and it has been increased in energy supply ratio of many countries.In shipping industry,as the emission standard of Tier III of IMO goes into effect,LNG is recognized as a preferred marine fuel of the future.Increased consumption of LNG promotes the transportation and mine of LNG,the LNG carrier,fuel tank,floating storage and regasification unit and fuel bunker vessel appears successively.However,as the consumption of LNG in transportation,storage and bunkering,partial loaded appears,which will bring the sloshing problem.Especially,when the resonance occurs,the liquid will impact the bulkhead of tank,produce the huge external moment,and increase the evaporatively of LNG.All these situations bring significant threat to the cargo containment system and stability of ship.Therefore,the simulation of sloshing,prediction of sloshing load and method of sloshing suppression has become the key of LNG tank design.Aiming at the most common tank type:LNG independent type C tank,the model experiment system was firstly designed and built.Based on the free oscillation and the sweep experiments,with extracting the global maximum and significant value,it was achieved that the deviation of resonant and natural frequency will increase as the filling condition decreasing.Through the model tank test,the wave pattern of liquid under longitudinal excitation was discussed,and the classification of wave system,which is influenced by tank roof,had been identified.The frequency and time domain and space distribution of sloshing load is also studied.With the application of FVM and VOF,three-dimensional liquid sloshing in independent type C tank was simulated.The liquid was considered as viscous and turbulent.Validated by sloshing experiment system,the platform of sloshing numerical simulation was built.For rapid assessment of sloshing load,based on model experimental validating,the rapid computational technology of sloshing load was presented.Combined with the determination method of filling condition,excitation frequency and amplitude of ship,the rapid computational method of sloshing load of tank in real ship was presented.Thus,the dangerous condition of sloshing was determined.The distribution of sloshing load in tank was given.By computation of sloshing condition of 1000 m3 fuel bunker vessel,the feasibility of this method was explained.According to the geometric structure of type C tank,ring baffle and perforated swash bulkhead were designed.The applicability of sloshing numerical simulation platform was validated by the experiment of sloshing model with anti-sloshing device.With the application of orthogonal analysis and the platform,the sensitivity of ring baffle geometrical parameter was discussed.The parameters,which had dramatical influence on sloshing suppression,and their best design plan were given.Besides,the critical height of ring baffle which has the best anti-sloshing efficiency was achieved.The suppression mechanism of main influence parameters was studied.The sloshing suppression mechanism of perforated swash bulkhead was researched by comparison with the sloshing experiment without bulkhead.The efficiency of sloshing suppression sensitivity of swash hole was researched numerically.It was found that diameter of swash hole had great influence on efficiency of restraining sloshing in half-loaded.Both two sloshing suppression devices were compared on anti-sloshing efficiency.Thus,the variation regularity of efficiency of two devices under different filling conditions was achieved.Above all,according to the key technology of LNG independent type C tank and its anti-sloshing devices design,based on the numerical simulation and model test,the sloshing characteristic and sloshing suppression mechanism were researched.The computational method of sloshing load of tank in real ship and design criterion of anti-sloshing device were presented.Thus,the direct computation of sloshing load of type C cargo hold and storage tank was achieved;the reference and guidance of proper design of anti-sloshing device and the technical support of revised relative rules were provided.