大幅横摇激励下液舱晃荡冲击载荷特性

Study on the Characteristics of Impact Loads of Liquid Sloshing under Large Amplitude Rolling Excitation

大型LNG(liquefied natural gas)船在非满载航行中可能引起强烈的砰击载荷,对结构安全造成威胁。基于数值模拟方法研究大幅横摇激励下晃荡压力与外激励的饱和非线性关系。采用基于有限体积法的CFD代码FLUENT求解器,通过动网格技术驱动液舱运动,并用VOF(volume of fluid)法追踪自由液面的非线性运动过程,数值预报典型装载率、大幅横摇激励下的晃荡压力特性及自由液面波形。研究结果表明,在小激励和中等激励范围内,随着横摇激励的增大,晃荡压力出现突然变大的现象;当横摇激励继续增大到某一阈值时,则随着横摇角增加,晃荡压力不再增大,而是呈现饱和现象;自由液面也呈现出非线性特征,液面振幅和激励幅值之间的关系不再成比例关系,而是出现复杂的响应形态;处于大幅横摇激励下的液舱,随着装载率提高,晃荡冲击压力会降低。

A large LNG(liquefied natural gas)vessel may cause intense slamming loads during non-full load operation,posing a threat to structural safety.This paper presents a numerical simulation-based study on the saturated nonlinear relationship between sloshing pressure and external excitation under large roll excitations.The paper utilizes the CFD code FLUENT based on the finite volume method to solve the governing equations.The dynamic mesh technique is employed to drive the motion of the liquid cargo and the Volume of Fluid(VOF)method is utilized to track the nonlinear motion of the free surface.Numerical predictions are made for the characteristic sloshing pressure and free surface waveforms under typical loading conditions and large roll excitations.The numerical results demonstrate that there is a sudden increase for impact sloshing pressure as the roll excitation increases in the range of small and moderate excitations.The impact sloshing pressure ceases to increase and exhibits a saturation phenomenon when the rolling angle surpasses a certain threshold.The free surface also exhibits nonlinear characteristics,where the relationship between the liquid surface amplitude and excitation amplitude is no longer proportional,but rather displays complex response patterns.For a liquid tank subjected to large roll excitations,the sloshing impact pressure decreases as the filling rate increases.