LNG独立C型液舱晃荡特性试验研究

Experimental study of sloshing pattern on LNG independent C type tank

与LNG运输船不同,LNG加注船的液舱会经常处于部分装载状态,故液舱晃荡问题必须予以考虑.由于目前LNG加注船主要采用独立C型液舱,针对该种形式液舱,使用模型试验,系统研究了不同载液高度、激励频率及激励幅值影响下的晃荡情况.讨论分析了其晃荡时自由液面的波形特征,对中间液深工况下,自由液面在舱顶的影响下出现的波形进行分类.通过对晃荡荷载的统计分析,发现产生最大荷载的激励频率与理论固有频率有所偏差,且该偏差会随着液位的升高而降低.此外,在荷载空间分布方面,载液高度为0.6 D_i(D_i为模型液舱直径)时,自由液面在封头处破碎严重,会对液舱封头上部产生较大冲击;而在0.8 D_i载液高度时,应充分考虑0.8f_n(f_n为理论固有频率)至1.2f_n激励区间内的顶部冲击荷载.

Being different from the LNG carrying ship , the tanks of LNG fuel bunker vessel arealways partially loaded,so the sloshi ng must be cons ider ed. Since independent C used in LNG fuel bunker vessel at present, model experiments with this type of tank are carried outfor sloshing research. The test conditions cover different filling levels, excitation frequencies and excitation amplitudes. The characteristic of free surface shape is discussed and analyzed.Furthermore, in the intermediate depth, classification of wave shapes, which is in fluenced by tank roof,is identified. With the statistical analysis of sloshing load, it is found that there is deviat io nbetween the excitation frequency inducing maximum load and theoretical natural frequency. Thisdeviation will reduce as the filling level increases. In addition, on aspect of spatial distribution of sloshing load,the free surface under 0. 6Di（Di is the diameter of the model tank ） breaks up and large impact pressure will be expected at upper part head ; un roof impact pressure with the excitation frequency between 0. 8/n（fn is theoretical natural frequency ）and 1. 2fn should be taken full account.