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1.
The present study focuses on the nonlinear behavior of pressure on the hull surface of a high-speed vessel in irregular waves, particularly the pressure responses of alternately wet and dry areas near the waterline and on the bow zone. The vessel has high deadrise angles that may be subject to slight impact and water pile-up effects. A series of experiments in regular and irregular head waves were conducted, and the validity of applying Volterra modeling was investigated. In a previous article using experimental data in regular waves, it was confirmed that the approximate third-order Volterra model adequately simulated the variation of pressure responses in regular waves of different steepness up to a wave amplitude with a wavelength ratio of 0.01, even for the highly nonlinear pressures acting on the abovementioned areas of the hull surface. In this article, further validation for the second part of the study was obtained using experimental data in irregular waves. The frequency response functions obtained from the previous study’s experimental data in regular waves were applied to the third-order Volterra model by combining the input of irregular waves to simulate the responses in irregular waves of sea state five. Then, the spectra and statistics were analyzed. For the motions, accelerations, and pressure responses in irregular waves (as well as for the simulated time histories) variance spectra and statistics such as cumulative distributions of peak values and probability density functions were compared with the experimental results. It was confirmed that even for highly nonlinear and non-Gaussian pressures on the abovementioned areas of the hull surface, the approximate third-order Volterra model simulates the pressure responses in irregular head waves up to a sea state of five with adequate accuracy on deterministic and statistical bases.  相似文献   

2.
This article presents a nonlinear time-domain simulation method for the prediction of large-amplitude motions of a Ro–Ro ship in regular oblique waves in an intact and a damaged condition. Numerical computations and model tests have been carried out to investigate the dynamic motion responses of Ro–Ro ship Dextra to various wave amplitudes at three different wave headings. The results of numerical and experimental investigations for stern quartering waves are reviewed. Comparisons between predictions and measurements show good agreement except in the roll-resonant region. Nonlinear effects are significant in horizontal modes of motion, and resonant roll motion, and there is strong coupling between all modes of motion in the roll-resonant region for large-amplitude responses. On the other hand, the time-domain simulation technique suffers from numerical drift in horizontal modes of motion as wave amplitude increases. This is due to nonlinear equations of motion and the lack of a restoring force and moment in horizontal motion. Received: April 30, 2002 / Accepted: August 9, 2002 Acknowledgments. II Programme of the European Community Commission under contract No. BRPR-CT97-0513. Address correspondence to: H.S. Chan (hoi-sang.chan@ncl.ac.uk)  相似文献   

3.
何军  蒋昌波  王珍  徐波 《水道港口》2009,30(5):305-310
通过规则波与T型防波堤相互作用的试验研究,揭示了T型防波堤底部所受冲击压强产生的原因。分析波浪冲击压强历时曲线、相对板宽对冲击压强沿水平板底部分布的影响,得到T型防波堤水平板冲击压强的特性以及2大影响因素:相对超高和波陡。应用因次分析的方法,推导出T型防波堤底板最大相对冲击压强计算的经验公式。结果表明,该公式计算结果与试验值吻合较好,有一定的适用性。  相似文献   

4.
弄清水下航行器内孤立波载荷形成机理是分析内孤立波对航行性能影响和控制研究的基础和前提。采用数值模拟方法深入分析模型位于内孤立波波面上方、穿越波面、位于波面下方3种情形下,模型受内孤立波流场水动力作用和分层密度差静力作用过程,对比不同潜深时纵向力、垂向力和俯仰力矩特性差异。研究表明,穿越波面的情况下,模型所处的流体密度变化,起了决定性作用,垂向力比纵向力大一个量级;穿越波面时,艏艉浮力不平衡,俯仰力矩有极大值和极小值出现;模型始终位于波面上方或下方时,受内孤立波流场的影响,其水动力性能也产生了明显的变化。  相似文献   

5.
A new computational fluid dynamics simulation method has been developed for the unsteady motion of a ship advancing in waves. The objective is to evaluate the added resistance and predict the performance of a ship in waves. In this study, a finite volume method, in the framework of a boundary-fitted grid system, is employed. The motion of the ship is solved with six degrees of freedom by using the hydrodynamic forces and moments obtained from the solution of the simulation method. The marker–density–function method is employed to calculate the nonlinear free surface. This method is applied to the coupled motion problem of heaving and pitching. Received for publication on Nov. 15, 1999; accepted on Nov. 18, 1999  相似文献   

6.
顶浪规则波中小水线面双体船纵向运动特性数值分析   总被引:1,自引:0,他引:1  
基于RANS方程和VOF模型求解船体粘性兴波流场,采用Overset技术处理船体运动,开展了小水线面双体船(Small Waterplane Area Twin Hulls,SWATH)迎浪规则波中运动响应特性及其产生机理的研究.通过数值计算结果与模型试验结果的对比分析,验证了本文方法的有效性;在此基础上,分析了船体运动响应曲线中各峰值产生的原因及片体间相互干扰对SWATH船在波浪中运动响应的影响,发现其中一个峰值出现的原因为遭遇频率接近船体运动固有频率,由此发生共振;另一个峰值的出现则可能与SWATH特殊的船型及附体配置有关.由于SWATH船片体间的水动力干扰效应,SWATH船在波浪中运动响应峰值较单个片体响应峰值明显减小,且出现的位置向低频方向移动.  相似文献   

7.
影响薄膜型LNG船大型化的一个关键问题是严重的液舱晃荡冲击压力以及由此引起的复杂和危险的结构动响应,至今模型试验是研究此类问题的最重要的方法。本文以某大型LNG船尺度较大和运动较剧烈的2号液舱为研究对象,设计了精细的三维晃荡试验模型,通过不同载液水平的系列规则和不规则运动激励的晃荡试验研究晃荡冲击压力特性;基于薄膜型液舱围护系统结构性能计算结果,设计四边简支铜板格分析液舱围护系统结构弹性效应;另外,还利用浪高仪测量液舱波面运动情况。试验结果表明不论规则运动激励,还是不规则运动激励,晃荡冲击压力幅值均表现出明显的随机性,工况可能产生远大于单自由度运动工况的晃荡冲击压力。晃荡冲击压力、应力和波面测量结果可为验证晃荡数值方法和液舱围护系统结构设计提供依据。  相似文献   

8.
在2层流体基本假设下,通过实验分别研究不同波浪入射角下,作用在半潜式平台立柱群和沉箱群上的内孤立波载荷特性.实验结果表明:在任意迎流角下,作用在立柱和沉箱各部分的载荷峰值均随波幅增大而线性增大,并且波的传播方向对力的峰值有显著影响.在相同波幅、相同分层比下,当来波方向与平台中纵剖面不平行时,沉箱群水平载荷峰值在迎流角为...  相似文献   

9.
系泊Spar平台波浪中耦合运动的数值模拟及模型试验   总被引:1,自引:0,他引:1  
为了研究恶劣环境载荷引起海洋结构物的非线性运动响应,文章基于三维时域格林函数理论,提出了采用时域物面非线性理论方法直接模拟系泊浮体时域耦合分析所需的水动力,建立了系泊浮体波浪中时域耦合运动的数学模型.该方法充分考虑了每时每刻浮体在瞬态波面下湿表面的变化,并计及平均水线面下瞬时空间位置的改变,系统研究了系泊Spar平台波浪中的耦合运动响应及系泊线张力.最后,将数值模拟结果与模型试验结果进行了比较,计算结果令人满意.  相似文献   

10.
破损进水舰船非线性横摇运动的实验研究   总被引:1,自引:0,他引:1  
通过设计破损舰船非线性横摇运动实验,对不同状态下的船模进行定频率变波高和定波高变频率的横摇激振试验,探讨舰船横摇运动的水动力特性随横摇频率和横摇幅角变化规律,分析Ⅱ类和Ⅲ类进水舱对破损舰船横摇运动的水动力特性的影响。运用混沌信号识别技术分析破损舰船进水后横摇运动的混沌特性,验证数值仿真的结果,预报破损舰船在规则波中的横摇运动的幅频响应和相频响应。  相似文献   

11.
为了研究超高压喷射条件下二次破碎喷雾模型对燃油雾化特性的影响,在AVL FIRE软件平台上对燃油喷雾过程进行数值模拟,搭建可视化喷雾闪光摄影试验台架。基于超高的燃油喷射压力对燃油的雾束发展形态进行了图像采集,利用试验结果对二次破碎喷雾模型进行修正,分析模型中主要参数对燃油雾化特性的影响。结果表明:KH波破碎时间常数 C2的减小有利于缩短喷雾贯穿距离,同时避免发生燃油撞壁现象;随着RT波波长常数C4的增大,二次破碎新生油滴的直径变大,雾化效果变差;由于首次破碎过程对二次破碎过程的制约作用,导致C4对喷雾计算结果的影响不像C2那样显著。  相似文献   

12.
规则波浪中舰船操纵与横摇耦合运动模拟及特性分析   总被引:2,自引:0,他引:2  
采用六自由度舰船操纵性方程与横摇波浪力矩耦合构成动力学模型,对舰船在规则波浪中的操纵与横摇耦合运动特性进行了模拟研究.其中操纵性方程采用MMG模型,波浪力矩由切片法计算,舰船航向按PD控制.模拟计算了某船正横规则波浪下保持航向的横摇运动,计算结果与单自由度理论结果进行了比较,其幅频曲线与相频曲线两者符合较好,间接证明了耦合构成动力学模型的有效性.在此基础上计算了不同浪向角和航速下的横摇运动,以横摇等值极坐标曲线表征舰船规则波浪中的横摇特性,从而给出了规则波浪下舰船耦合动力学所描述的运动特征.  相似文献   

13.
A method for the prediction of slamming loads on ship hulls is presented and validated for a 20-knot, 120-m car carrier. A nonlinear strip theory is used to calculate the relative motions of ship and wave. The relative vertical and roll velocities for a slamming event are given as input to the slamming calculation program, which is based on a generalized two-dimensional Wagner formulation and solved by the boundary element method. The method is fast and robust. Model tests of a car carrier have been carried out in regular head, bow, and bow quartering waves of various heights. Slamming on two panels in the upper part of the bow flare has been studied. It has been found that the water pile-up around the bow due to the forward speed of the vessel significantly increases the slamming pressures. A simplified way of including this effect is presented. When the calculated slamming pressures are corrected for 3D effects, they compare well with the measured data. Since the effect of the wave elevation due to the forward speed and the effect of three-dimensional flow act in opposite directions, excluding both of them produced results that also agreed quite well with the experiments, especially for the most severe slamming events.  相似文献   

14.
文章研究了多蛋形交接耐压壳屈曲行为。基于壳体开孔处的变形量与完整壳体一致的设计理念,优选多蛋壳结构参数,制作多蛋壳比例模型,并对其制作误差进行了检测。此外,还进行了静水压力试验,验证真实多蛋壳破坏形式,检验环肋参数的合理性,比较了考虑真实形状和厚度的非线性有限元分析结果。结果表明:基于变形协调理念设计的多蛋壳,最终破坏远离环肋交接处,蛋形壳单元破坏形式及载荷与完整单蛋壳基本相同,试验验证了多蛋壳继承了完整蛋形壳较好的耐压特性;基于弧长法的数值计算与试验结果具有良好一致性,考虑真实形状和厚度的非线性有限元分析可用于分析预测真实壳体的屈曲特性。  相似文献   

15.
周俊 《中国海事》2010,(12):53-53
文中通过对渔船A被撞沉没后肇事船舶逃逸案件调查,分析了肇事逃逸案件的特点及原因,并提出了相关建议,旨在加强我国海上肇事逃逸追查工作。  相似文献   

16.
在船坞灌水虹吸管的水力学试验的基础上,研究了虹吸廊道驼峰断面上的负压特性及其压强分布,驼峰断面上的负压未超出规范所允许的范围.试验结果表明,虹吸灌水廊道原型设计合理.  相似文献   

17.
穿浪双体船作为一种新船型,逐渐在近海高速客运领域中发挥重要作用。研究穿浪双体船在不同海况条件下的摇荡运动规律具有重要意义。本文采用修正切片法计算某穿浪双体船的纵摇、垂荡以及横摇运动的幅值响应函数,并采用谱分析的方法统计计算其在不同海况条件下的摇荡运动规律,通过零航速时计算结果与试验结果的比较,验证了本文计算方法的正确性。最后,对本文计算对象在不同海况条件下的摇荡运动规律进行了分析。  相似文献   

18.
Ships which have large structures above water surface, such as pure car carriers (PCCs) and container vessels, have large speed reduction by wind pressure. In the present study, the running speed of a large PCC with two or more sails for using wind power is simulated. The simulated results demonstrate that the ship can keep a constant service speed even in winds of 20m/s except head and bow winds. This sail system can shorten annual average navigation time by about 4 hours per voyage.  相似文献   

19.
船舶顺浪航行的纯稳性损失研究,已成为国际航海界和国际海事组织(IMO)关注的课题之一.在Ю.И.涅查耶夫根据28艘渔船和运输船船模水池试验的船舶顺浪纯稳性损失计算方法的基础上,提出了扩展模式,扩大了其适用范围,并给出了大长宽比(船长/船宽)舰艇纯稳性损失的算例,同时实现了该扩展模式的程序化,生成了实用化的软件.最后通过与CFD试验方法和一般理论计算法所得结果的对比,验证了该扩展模式计算结果的可信度.  相似文献   

20.
This paper presents an effective scheme for computing the wave-induced hydroelastic response of a very large floating structure, and a validation of its usefulness. The calculation scheme developed is based on the pressure-distribution method of expressing the disturbance caused by a structure, and on the mode-expansion method for hydroelastic deflection with the superposition of orthogonal mode functions. The scheme uses bi-cubic B-spline functions to represent unknown pressures, and the Galerkin method to satisfy the body boundary conditions. Various numerical checks confirm that the computed results are extremely accurate, require relatively little computational time, and contain few unknowns, even in the region of very short wavelengths. Measurements of the vertical deflections in both head and oblique waves of relatively long wavelength are in good agreement with the computed results. Numerical examples using shorter wavelengths reveal that the hydroelastic deflection does not necessarily become negligible as the wavelength of incident waves decreases. The effects of finite water depth and incident wave angle are also discussed.  相似文献   

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