大型LNG船波激振动模型试验研究

Experimental Investigation of Springing Responses of a Large LNG Carrier

尽管LNG船波浪总体载荷的研究在数值方法和模型试验研究方面均有文献可考,但是大型化后的LNG船其波激振动特性的研究仍不多见,考虑液舱晃荡作用对整体波浪载荷尤其是对波激振动影响的试验研究更为缺乏。在中国船舶科学研究中心耐波性水池和拖曳水池对一艘大型LNG船分别进行了两种缩比的模型试验,研究了液舱中液体晃荡和船体刚度变化对总体载荷的影响。试验研究发现了波浪载荷中倍频成分引起的非线性波激振动现象,并且在斜浪中存在类似于垂向波激振动的横向和扭转波激振动。液舱中液体的晃荡总体上减弱了船体的波激振动响应。船体刚度的减小引起船体结构的水弹性效应被急剧放大,从而导致了严重的波激振动现象。最后对本文所述的模型试验进行了不确定度因素分析,并给出了相关结论。

Although the investigation of wave loads of LNG carriers by numerical and experimental methods can be found from some references, the available experimental data of springing responses of large LNG carders seems rare. Up to now, the experimental investigation of sloshing effects to global wave loads, especially the springing responses, is still blank. Experiments for four models of a large LNG carder with two scales have been conducted in seakeeping and towing tank of china ship scientific research center （CSSRC）. The sloshing effects and that from the variation of hull girder stiffness have been studied by these model tests. It can be found from the experimental investigation that the harmonic components in wave loads had induced the springing responses. The similar resonant vibrations such as horizontal and torsional springing responses have also been found in oblique waves. As a whole, sloshing in liquid tank has taken some decreasing influence to springing responses. The hydroelastic effect is drastically enlarged because of the reduction of hull girder stiffness. And consequently, severe springing responses appeared. The uncertain factors in model tests are discussed and some conclusions are recommended in the end of this paper.