Nonlinear hydrodynamic forces acting on an offshore structure n waves

波浪作用在海上结构上的非线性水动力

• 批准号: 07455401
• 负责人: KINOSHITA Takeshi
• 金额: $ 4.54万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455401/
• 关键词: wave drift force; wave drift damping; slow drift motion; springing; ringing; wave drift force; wave drift damping; slow drift motion; springing; ringing

Offshore structures moored in waves often undergo slow drift motions. Because the restoring force offered by the mooring system is weak, the natural period is long enough to match up with the slowly varying nonlinear wave excitaion, which will cause resonance with large amplitude of horizontal excursion. It is critical for the design of the mooring devices to predict these drift motions precisely. It is well konown that the slow drift damping plays a key role to determine the amplitude of the drift motions when the resonamce is triggered. Previous works show that the so-colled wave drift damping makes an important contribution sometimes even dominant compared with the other components of the slow drift damping such as viscous damping and mooring damping.First of all concerning this topic, the probelm of a single circular cylinder freely oscillating in both waves and slow current was considered. Series calculations of wave drift damping were made to show the effects of cylinder draft an … More d water depth. Then the ineraction among multiple circular cylinders was considered. The comparison of calculated results with the experimental data were presented. In these works, the method of eigenfunction expansion was used to solve the boundary value problem. It has a limitation to be applied to bodies with arbitrary shapes.On the other hand, the boundary element method is also used to solve the problem of floating structures in both waves and slow current. The method is applied to a circular cylinder. Calculated results are compared with those by the semi-analytical method to validate the method. Then a series calculation are carried out on ellipsoids with various breadth and draft to examine the effects of body shape on the wave drift damping.High-frequency nonlinear wave excitation is also studied. Double frequency and triple frequency excitations in regular wave trains are computed by an eigenfunction expansion method. They may cause springing and ringing phenomena of a tension leg pratform. Less

停泊在波浪中的海上结构经常发生缓慢的漂移运动。由于系泊系统提供的恢复力很弱，因此自然周期足够长，足以与慢速变化的非线性波兴奋相匹配，这将引起大型水平偏移放大器的共鸣。对于系泊设备的设计，精确预测这些漂移运动至关重要。 It is well known that the slow drift damping plays a key role to determine the amplifier of the drift motions Previous works show that the so-colled wave drift damping makes an important contribution sometimes even dominant compared with the other components of the slow drift damping such as viscous dance and mooring dance.First of all concerning this topic, the probem of a single circular cylinder free oscillating in both waves and slow current was considered.进行了波漂移舞的串联计算，以显示圆柱草稿的影响和更多的水深。然后考虑了多个圆柱体之间的绝缘材料。提出了计算结果与实验数据的比较。在这些作品中，使用本本特征扩展方法来解决边界价值问题。它有一个限制，可以应用于任意形状的身体。另一方面，边界元素方法还用于解决波和慢速电流中的浮动结构问题。该方法应用于圆柱体。通过半分析方法将计算结果与验证该方法的结果进行比较。然后，在具有各种宽度的椭圆形上进行了一系列计算，以检查体形对波漂移阻尼的影响。高频非线性波兴奋也是研究的。常规波列中的双频和三重频率兴奋是通过特征功能扩展方法计算的。它们可能会导致张力腿打印机的弹性和铃声现象。较少的