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On estimation method of diffraction forces on cylindrical structures in multi-directional waves

多向波中圆柱结构绕射力的估计方法

基本信息

批准号：
08555128
负责人：
IWATA Koichiro
金额：
$ 2.94万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

Nonlinear wave diffraction due to cylindrical structures in a multidirectional irregular wave field and the wave forces acting on the cylinder are investigated experimentally and theoretically. An estimation technique for the diffraction forces on the cylinders is introduced in this work. To discuss the mechanism of both the wave field and its induced forces on the cylinders, extensive experiments have been conducted in case of a regular wave train and two-crossing waves. The followings can be concluded based on the project work.(1) The theory obtained by MacCamy and Fuchs gives reasonable estimate of the diffraction wave force on a cylinder in case of regular wave field. However, the theory is inadequate in estimating the diffraction wave force on a cylinder in unidirectional irregular wave. In the multidirectional wave field, the estimation of the diffraction wave forces by the theory has low accuracy.(2) The spreading parameter affects the diffraction wave force in general. The wave … More force in the principal direction does not always increase with increasing the spreading parameter. Moreover, it is found that the wave force on a cylinder constructed on a slope shows different characteristics from that in a constant water depth because of wave refraction.(3) Wave forces acting on a cylinder in an array of two cylinders are influenced by the spacing between the cylinders and the incident wave period rather than the spreading parameter in case of weakly directional wave field. As the directional spreading of the incident waves becomes appreciable, the effect of the interaction between diffracted waves from individual cylinders becomes less significant.(4) As the spacing between the cylinders in an array becomes smaller, the wave height in the area between the cylinders increases. This enlarges the wave pressure on the cylinder surface. The wave height outside the cylinder array seems to be independent of the cylinder's spacing, however, this depends on the directionality of incident waves such that it becomes larger when increasing the directional spreading. This may result in larger wave pressures on the cylinder surface in a multidirectional wave field.(5) Except for the impulsive wave breaking force, which is not discussed in this project, it can be judged that the effect of the directional spreading should be properly considered in estimating the design wave force on cylindrical siructures.(6) For more detailed discussions of the nonlinear wave diffraction and wave forces, the time domain analysis may be necessary. Moreover, the velocity field in a multidirectional wave should be investigated with respect to the wave height distribution. These deemed necessary for future investigations of this problem. Less

从实验和理论上研究了多向不规则波浪场中圆柱体结构的非线性波浪绕射和作用在圆柱体上的波浪力。本文介绍了圆柱体绕射力的一种估算方法。为了探讨波浪场及其对圆柱的作用力的机理，在规则波列和双交叉波的情况下进行了大量的实验。(1)根据MacCamy和Fuchs的理论，对规则波场作用于圆柱体的绕射波浪力进行了合理的估计。然而，该理论在估算单向不规则波中圆柱体所受的绕射波浪力时还存在不足。在多向波浪场中，用理论估算绕射波浪力的精度较低。(2)传播参数一般影响绕射波浪力。The Wave…主方向上的更多力并不总是随着扩散参数的增加而增加。此外，由于波浪的折射，作用在斜坡上的柱体上的波浪力表现出与恒定水深中不同的特征。(3)在弱方向波场情况下，作用于两柱阵列中的柱体上的波浪力受柱间间距和入射波周期的影响，而不受波浪力传播参数的影响。随着入射波的定向传播变得明显，来自单个柱体的衍射波之间的相互作用的影响变得不那么显著。(4)随着阵列中柱体之间的间距变小，柱体之间区域的波高增加。这增大了圆柱体表面上的波动压力。圆柱阵列外的波高似乎与圆柱的间距无关，但这取决于入射波的方向性，因此随着定向传播的增加，它会变得更大。这可能会在多向波浪场中对圆柱体表面产生更大的波浪压力。(5)除了本项目中没有讨论的冲击破波力外，可以判断，在估算圆柱体结构的设计波浪力时，应适当考虑定向传播的影响。(6)对于更详细的非线性波浪绕射和波浪力的讨论，可能需要进行时域分析。此外，还应从波高分布的角度研究多向波中的速度场。这些都被认为是今后对这个问题进行调查所必需的。较少