超大型集装箱船非线性波浪载荷预报

Prediction of Nonlinear Wave Loads of Ultra Large Containerships

如今大型集装箱船的水弹性分析对于结构设计已十分重要。随着集装箱船的大型化,颤振现象由于其对于结构设计载荷分析的影响,已成为结构设计的重要考虑因素。本文给出了基于三维频域格林函数和动量定理的耦合时域水弹性方法,介绍了频率等效的分段变截面龙骨梁非线性波浪载荷测试系统,并开展了一系列不规则波试验,基于10000TEU集装箱船的实验结果进行了理论计算对比和有效性验证。依据对比结果分析了波面高程、船舶垂向运动响应和垂向剖面载荷响应统计值的不对称性,理论计算和试验结果吻合良好。基于此进行了船舯剖面垂向弯矩非线性长短期分析,将长期分析结果与船级社规范值进行对比,二者吻合良好。

The importance of hydroelastic analysis of large and flexible containerships of today is pointed out for structure design.As the size of containerships increases,whipping phenomena is one of the important design considerations due to its significant effect on design wave loads analysis.In this paper,a 3 D nonlinear hydroelasticity theory was introduced which utilizes a 3-D Green function method and a 2-D momentum model coupled in time domain.A model system for measurement of nonlinear wave loads which is composed of a backbone and segmented container ship model is already built and applied to a series of large ship models,in which the natural frequency of vertical bending is matched using a beam with rectangular-shaped variable cross-section.A series of model tests are carried out for selected cases of whipping in irregular waves.The computational results are compared with those of a model test of a 10000 TEU containership.Verifications and validations between model test results and theoretical calculation are conducted.Discussions are focused on the asymmetry of wave elevation,vertical ship motion and vertical sectional loads responses,which are observed and calculated in irregular wave conditions,and they show good agreement between experimental and simulated results,based on which the design vertical bending moment at midship can be obtained by using the nonlinear short-term and long-term analysis and the comparison between direct calculation and classification society rules shows good agreement with each other.