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Prediction of deck wetness, divergent bow waves on fine ships: Nonlinear numerical studies.

机译:甲板湿度的预测,细小船上的发散弓形波:非线性数值研究。

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摘要

Based on a nonlinear slender body theory approach, numerical methods are here developed and successfully applied to solve one the most difficult ship seakeeping problems--the prediction of the deck wetness of ships moving through heavy seas. The simulation of deck wetness on a frigate model using the method developed here agrees very well with the experimental data. The nonlinear slender body {dollar}2D+T{dollar} approach is thereby proved to be an effective tool in dealing with strong nonlinear free surface flow problems; continuous time domain pictures of the bow wave evolution during motions in oncoming waves is achieved through these simulations. The relationship between deck wetness and ocean parameters is found; the effect of dynamic effects (dynamic rise) on the water elevation is shown to be of critical importance.; Divergent waves are also studied in detail utilizing a high resolution {dollar}2D+T{dollar} simulation. The effects of changes in speed, beam, draft and rake stem angle are studied and discussed for Wigley-like hulls. Satisfactory comparisons are made with fully non-linear 3-D calculations by Hoyte Raven with RAPID, as well as with experimental measurements for a Todd Series 60 model. The present simulations confirm the non-linear characteristics of the bow waves, earlier observed by W. Froude, Inui, and Miyata. An explanation is offered here for these observations in terms of the narrow wave spectra arising from interference between the two sides of the hull at the location of the splash peak. For normal ship slenderness {dollar}(B/L=0.1{lcub}-{rcub}0.2){dollar} the divergent bow wave crests tend to be straight due to the narrow spectrum, and the wave crests are very steep, resembling Stokes limiting waves, and/or breaking. Strong breaking has a similarity to the breaking of two dimensional progressive waves: an energetic plunging jet forms.; The first bow wave's crest line angle decreases with increase of speed, while larger beam-length ratios produce larger bow waves which break more easily. The slenderness of the hull, B/L, is a dominant factor in determining not only the steepness, but also the wave patterns of divergent waves. For normal B/L the nonlinear simulations indicate that there is a narrow spectrum for divergent waves with a concentration of energy at a particular wave number associated with the beam. Numerical simulation of the bow wave patterns are also carried out via Michell's linear theory and comparisons are made with the nonlinear simulations; typical linear Kelvin wave patterns appear, and despite the obvious differences between the linear and nonlinear simulation results, similarities between the wave patterns are shown to exist.; Finally, limited studies of stern waves are made. For closed hulls, the numerical results indicate that the stern wave originates in the gravitational collapse in the "rooster tail" which is thrown up behind the hull.
机译:在非线性细长体理论方法的基础上,本文开发了数值方法,并成功地将其应用于解决最困难的船舶海上维护问题之一-预测在重海中航行的船舶的甲板湿度。使用此处开发的方法在护卫舰模型上对甲板湿度进行模拟与实验数据非常吻合。因此,非线性细长体{dollar} 2D + T {dollar}方法被证明是解决强非线性自由表面流问题的有效工具。通过这些仿真,可以得到在迎面而来的海浪运动期间船首海浪演变的连续时域图片。发现甲板湿度与海洋参数之间的关系;动态影响(动态上升)对水位的影响被证明是至关重要的。还利用高分辨率{dollar} 2D + T {dollar}模拟对发散波进行了详细研究。研究和讨论了类似威格利式船体的速度,横梁,吃水和前倾角的变化的影响。 Hoyte Raven使用RAPID对完全非线性的3-D计算以及对Todd Series 60模型的实验测量进行了令人满意的比较。目前的模拟证实了弓形波的非线性特征,这是W. Froude,Inui和Miyata早先观察到的。对于这些观察,这里将根据在飞溅峰位置处的船体两侧之间的干涉所产生的窄波谱进行解释。对于正常的船舶细长度,{dollar}(B / L = 0.1 {lcub}-{rcub} 0.2){dollar}由于频谱较窄,弓形波峰趋于平直,并且波峰非常陡峭,类似于斯托克斯限制波和/或破坏。强破裂与二维渐进波的破裂相似:高能量的急速喷射形式。第一个弓形波的波峰线角随速度的增加而减小,而较大的光束长度比会产生较大的弓形波,更容易破裂。船体的细长度B / L不仅是决定陡度的主要因素,而且也是决定发散波的波形的主要因素。对于正常的B / L,非线性模拟表明,发散波的频谱很窄,能量集中在与波束相关的特定波数处。还通过米歇尔线性理论对船首波模式进行了数值模拟,并与非线性模拟进行了比较。出现了典型的线性开尔文(Kelvin)波形,尽管线性和非线性仿真结果之间存在明显差异,但波形之间存在相似之处。最后,对船尾波进行了有限的研究。对于封闭的船体,数值结果表明,船尾波起源于引向船体后面的“公鸡尾巴”中的重力塌陷。

著录项

  • 作者

    Wu, Ming.;

  • 作者单位

    University of California, Santa Barbara.;

  • 授予单位 University of California, Santa Barbara.;
  • 学科 Engineering Marine and Ocean.
  • 学位 Ph.D.
  • 年度 1997
  • 页码 188 p.
  • 总页数 188
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 海洋工程;
  • 关键词

  • 入库时间 2022-08-17 11:48:59

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