Experimental Investigation of the Nonlinear Effects on the Statistics of Vertical Motions and Loads of a Containership in Irregular Waves
Experimental Investigation of the Nonlinear Effects on the Statistics of Vertical Motions and Loads of a Containership in Irregular Waves
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发表时间：
2004-06
影响因子：
1.4
通讯作者：
N. Fonseca;C. Soares
中科院分区：
文献类型：
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作者：
N. Fonseca;C. Soares
船舶结构的设计大多基于经验设计规则。然而，随着计算资源变得更快、更便宜，越来越倾向于应用更多基于直接计算的过程。这些基于结构波浪引起的载荷的水动力计算以及海浪和引起的船舶响应的适当随机特征。船舶结构强度将取决于其使用寿命期间预期的极端波浪引起的船体梁载荷。在线性水动力载荷的情况下，不规则航道中的预期最大结构载荷可以通过频域中的线性势方法和高斯过程的峰值瑞利分布来计算（例如，Fukuda 1967，Guedes Soares & Moan 1991）。然而，众所周知，至少具有精细形状或小块系数的船舶会对波浪做出非线性早期响应。对于这些船舶，垂直结构载荷高度不对称，下垂峰的幅度比中拱峰更大。因此，原则上不能应用传统的线性随机过程。设计非线性波浪结构荷载必须通过时域非线性代码和适当的极值分布来计算。完全非线性方法正在开发中，以解决完全非线性三维边值问题，要么假设无粘流（Subramani & Beck 2000），要么使用纳维-斯托克斯雷诺平均解（Xing et al 2001）。然而，完整的解决方案尚未实现。数值复杂性和计算工作量巨大，并且预计此类方法不会在中期内用于实际应用。替代方案是应用部分非线性方法，该方法结合了假设的对船舶响应最相关的非线性贡献。已经提出了几种简化的非线性方法，它们可能基于条带方法（Xia & Wang 1997，Fonseca & Guedes Soares 1998a）或面板方法（Lin et al 1996，Huang & Sclavounos 1998）。然而，这些类型的程序必须根据实验结果进行验证。国际船舶和近海结构大会 (ISSC)2000 年关于极限载荷的委员会 VI.1（Jensen 等人 2000）报告了非线性耐波性方法和技术的最新进展。
, the design of the ship structures is mostly based onempirical design rules. However, as the computational resourcesbecome faster and cheaper, there is a growing tendency to applymore procedures based on direct calculations. These are based onhydrodynamic calculation of structural wave-induced loads to-gether with a proper stochastic characterization of the ocean wavesand of the induced ship responses. The ship structural strength willdepend on the expected extreme wave-induced hull-girder loadingduring its operational lifetime.In the case of linear hydrodynamic loads, the expected maxi-mum structural loads in irregular seaways can be calculated by lin-ear potential methods in the frequency domain and peak valueRayleigh distributions for Gaussian processes (e.g., Fukuda 1967,Guedes Soares & Moan 1991). However, it is known that at leastships with fine forms, or small block coefficients, respond nonlin-early to the waves. For these ships the vertical structural loads arehighly asymmetric with sagging peaks presenting larger magni-tudes than the hogging peaks. Thus, the conventional linearstochastic procedure cannot in principle be applied. Design nonlin-ear wave structural loads must be calculated by time domain non-linear codes together with appropriate extreme value distributions.Fully nonlinear methods are under development to solve thefully nonlinear three-dimensional boundary value problem, eitherassuming inviscid flow (Subramani & Beck 2000) or using Navier-Stokes Reynolds averaged solutions (Xing et al 2001). However,complete solutions have not yet been achieved. The numericalcomplexity and computational effort are enormous, and it is notforeseen that such methods will be used for practical applicationsin the medium-term future.The alternative is to apply partially nonlinear methods that in-corporate the assumed most relevant nonlinear contributions forthe ship responses. Several of these simplified nonlinear methodshave been proposed, which may be based on strip methods (Xia &Wang 1997, Fonseca & Guedes Soares 1998a) or panel methods(Lin et al 1996, Huang & Sclavounos 1998). However, these typesof procedures must be validated against experimental results.The International Ship and Offshore Structures Congress (ISSC)2000 Committee VI.1 on Extreme Loads (Jensen et al 2000) reportsthe recent developments on nonlinear seakeeping methods and