基于HHT变换的晃荡实验冲击荷载特性分析研究

Research on characteristics of experimental sloshing impact load based on HHT

对于储液舱内的液体晃荡问题,室内模型实验是研究晃荡荷载特征及规律最为有效的研究方法。本文引入HHT(Hilbert-Huang Transform,希尔伯特黄变换)-EMD(Empirical Mode Decomposition,经验模态分解)方法进行晃荡冲击时程的频域特性分析研究,首先采用EMD将晃荡冲击时程分解为多个IMF(Intrinsic Mode Function,本征模态函数),然后通过HHT对IMF分量进行谱分析,结果表明HHT-EMD方法能够用于晃荡冲击时程的分析和处理。此外,由于晃荡冲击时程波动性复杂所产生的IMF分量较多,通过与晃荡实验图像对比分析发现,冲击过程中能量主要集中于高频和低频部分,而且分量中低阶部分代表晃荡现象的高频噪声,次阶分量代表晃荡冲击能量部分,高阶部分代表晃荡液体的运动趋势。在此基础上对晃荡时程进行了去噪声处理。上述方法的引入为晃荡荷载研究提供了有益的参考。

In the ocean oil-gas engineering field,the development of FLNG(Floating Liquefied Natural Gas)and LNG(Liquefied Natural Gas)ships has attracted more attention recently,which will play an important role in the LNG(-163℃)marine exploitation and the global transportation.GTT membrane tank is one of key components of FLNG for storing LNG.However,the sloshing problem is considered as a crucial factor in the design of LNG tanks to be partially filled.Considering strong nonlinearity of sloshing load time-history,HHT(Hilbert-Huang Transform)-EMD(Empirical Mode Decomposition)is introduced to make the frequency domain analysis,including signal scale characteristics and instantaneous frequency information based on the data in the largest scale model tank.The results indicate that in the complicated pressure signal,the highest order components represent the high frequency noise,the higher order components carry the most energy of sloshing load and the low order components represent the trend of the sloshing liquid surface.Based on the above results,the pressure signal is reconstructed.The research achievement can serve as a useful reference for the solution of sloshing problems of large-scaled LNG tanks.