双排舱型LNG-FSRU频域内液舱晃荡研究

Investigation on Sloshing Effects of Tank Liquid on the LNG-FSRU Fitted with Two Rows Arrangement of Cargo Tanks in Frequency Domain

利用液舱晃荡-水动力耦合方法,对27 000m^3双排舱型液化天然气浮式储存气化装置(LNG-FSRU)液舱晃荡下水动力性能在频域内进行了研究,在各典型工况下对考虑和不考虑液舱晃荡作用的船体运动进行了比较和分析。分析认为区别于对单排舱横摇的显著影响,晃荡对双排舱横摇影响较小,对纵荡和横荡影响较大。随着液舱装载率的增加,纵荡和横荡对晃荡的响应频率相对于液舱在此方向的固有频率的偏移增大。结合选取的波谱和环境参数对液舱内动压力进行了短期预报,得到不同装载率下货舱内点的动压力极值分布,为货舱结构分析提供依据。分析发现极限动压力来源和分布形状与液舱装载率有关,不同装载率下自由表面处极限动压力极值大小与液舱晃荡作用下船体运动的响应强弱不一致,低装载10%附近时液舱晃荡最为剧烈。

The hydrodynamic analysis with sloshing effect is carried out for a 27 000 m^3 liquefied natural gas floating storage and regasification unit(LNG-FSRU)fitted with two rows arrangement of cargo tanks through the method of dynamic coupling of seakeeping and sloshing.Comparison is performed on the ship's motion of typical loading conditions with and without considering sloshing effects of tank liquid.The analysis on the effect of sloshing shows that apparently different from the main response in roll for the single row arrangement of cargo tanks,two rows arrangement of cargo tanks results in less effect in roll,but mainly in surge and sway.The shifting between the response frequencies and the natural frequencies of cargo tanks increases with the increase of the filling level of cargo tanks.Short term analysis on dynamic pressure in tank is also performed with the expected wave spectra and environmental conditions in order to get the extreme responses.Distribution of dynamic pressure in tank is finally figured out for further analysis of structural strength of the cargo tanks.The analysis shows that the distribution of dynamic pressure in tank is related to the filling level of the cargo tanks.The order ranked on typical loading conditions as per the maximum dynamic pressure at free surface is not completely consistent with which ranked in accordance with the response of the ship motion with considering sloshing effects of tank liquid.Sloshing effect is the most onerous at the low filling level about 10%.