五体船兴波阻力预报和减阻设计遗传算法

以线性兴波阻力薄船理论Michell积分和科钦函数线性叠加原理为基础,采用正交切比雪夫多项式拟合片体横剖面面积曲线,得出单体船、三体船和五体船通用的线性兴波阻力数值计算公式。据此,对不同侧体位置布局的Wigley五体船算例的兴波阻力进行系统的计算,并分析侧体位置布局对五体船兴波阻力的影响规律。在此基础上,进一步应用遗传算法对五体船的侧体位置布局进行减阻设计,得到五体船在计算航速下的侧体位置布局减阻设计方案。研究表明,所提五体船兴波阻力线性理论算法以及侧体位置布局减阻设计遗传算法均有效可行。     

SWATH阻力的数值计算方法及其性能试验

用七次幂多项式拟合片体线型和主体横剖面面积曲线，以线性兴波阻力理论为基础计算兴波阻力；以“相当平板’’假设为基础计算摩擦阻力；采用“1 k”的方法计算形状阻力，提出了SWATH阻力的完整方法。与船模试验结果比较得出：采用本方法预报SWATH的阻力比较接近实际情况。     

小水线面双体（SWATH）船兴波阻力计算及其船型优化

本文分三部分。第一部分采用线性分布源汇来代替片体并以第一类chebyshev多项式拟合横剖面面积曲线和支柱水线,。用递推公式求解积分,提出了SWATH船兴波阻力一个改进的计算方法,第二部分讨论了在给定下部主体的前提下,通过选择支柱的参数使阻力达到最低的优化问题;第三部分给出了有关数值计算结果和模型试验的结果,证实了本文所提出的方法的可靠性。     

一种生成小水线面双体船型线的简单方法

基于切比雪夫多项式和现有SWATH的统计资料,从SWATH主体及支柱特征出发,提出一种生成支柱水线方程和主体横剖面面积曲线的比较简单的方法,并将计算结果与实船线型值进行比较,表明计算精度能满足设计实践的要求,可作为初步设计阶段生成SWATH水下型线之用。     

穿浪双体船片体间距优化

实现了一种基于面元法的穿浪船兴波阻力和兴波波形的势流计算方法,数值计算了不同片体间距的穿浪双体船的兴波阻力与兴波波形.剩余阻力的计算与实船的剩余阻力曲线趋势较符合,片体间距的数值优化结果与模型试验吻合,其计算结果对实船船型参数的选择和优化设计有一定的指导意义.     

高速三体船兴波阻力与片体布局优化研究

本文据线性兴波阻力理论推导了辅船体与主船体水下体积不相等情况下的兴波阻力计算公式,据此以数学船型作为片体对高速三体船片体兴波干扰规律、兴波阻力曲线规律进行了研究,并采用简单枚举与等值线图谱相结合的方法对片体布局优化问题进行了探讨.     

基于线性兴波阻力理论的三体船中体船型优化

提出将线性兴波阻力帐篷函数法推广应用于三体船的方法。推导出确定侧体构型下的三体船线性兴波阻力帐篷函数法表达式及其中体船型优化的二次规划法计算模型。按该方法对数学三体船和工程应用三体船算例进行兴波阻力计算,将计算结果与模型试验结果进行对比验证,结果表明该方法计算三体船兴波阻力具有足够的精度。采用基于此兴波阻力表达式的中体船型优化二次规划法计算模型,对上述工程应用三体船中体船型进行了兴波阻力减阻优化计算,结果表明中体船型优化获得的兴波阻力减阻效果约达10%。     

用Rankine波幅函数预报高速三体／五体船主体与侧体的兴波阻力干扰

基于兴波阻力的薄船理论,作者曾提出用兰金体波幅函数(RWAF)代替实际船型的波幅函数,确定了高速双体船片体间的阻力干扰因子,从而可计算得到双体船的兴波阻力.本文将该方法用于高速三体船侧体与主体之间的兴波阻力干扰计算,以探讨主、侧体尺度及相对位置变化对于兴波阻力干扰因子τO、τOM的影响及其变化规律.基于这一研究结果,可实现用单体船阻力的实验资料,经过侧体、主体间的兴波干扰影响理论修正,来估算高速三体船的阻力;同时可用于对于最小阻力三体船片体尺度与布局之优化.     

基于兴波阻力的三体船片体位置快速优化方法

三体船片体位置优化的工作量很大,不仅要考虑片体间的横向距离,也要考虑片体间纵向距离.为快速优化三体船的片体位置,基于Noblesse细长体理论,按照一阶Kochin函数的表达式,在指数函数展开分离变量方法的基础上,本文推导了三体船兴波阻力的计算公式,并根据这些公式实现了三体船兴波阻力的快速计算.数值计算与模型试验相吻合.数值计算结果和模型试验结果均显示,三体船的片体位置对兴波阻力有很大影响.     

小水线面双体船兴波阻力数值仿真研究

建立小水线面双体船的基本计算模型,分别改变片体吃水、主体长径比、片体间距、支柱长度和支柱与主体最大横剖面间纵向距离,采用SHIPFLOW软件对兴波阻力系数进行数值仿真计算。根据计算结果,分析各船型要素对兴波阻力系数的影响规律,为小水线面双体船的船型设计提供参考。     

浅谈近岸、浅海海域波浪对船舶的危害——A轮沉没引发的思考

近岸，浅海海域的波浪与深海海域的波浪性质相异，航海驾驶人员必须特别重视，以防其造成船舶的浪损或更严重的海事发生。     

弹性钢索中纵波与弯折波的耦合作用研究

针对目前研究弹性钢索中应力波传播规律时忽略纵波与弯折波相互作用影响的问题,文章从理论研究的角度介绍了纵波与弯折波相互耦合作用的机理和计算方法,并采用该方法进行了弹性钢索四次冲击应力的分析计算。结果显示,计算结果与文献中试验观察现象一致,从而验证了该计算方法的有效性。     

Second-order wave run-up on a vertical cylinder adjacent to a plane wall based on the application of quadratic transfer function in bi-directional waves

A numerical model was developed in this study to simulate the wave diffraction caused by an arbitrarily shaped structure in the presence of bi-directional incident waves based on a higher-order boundary element method (HOBEM). Based on the developed model, the wave elevation quadratic transfer function (QTF) in bi-directional waves, which is defined as the second-order wave elevation caused by two incident waves of unit amplitude from two directions, can be determined. The developed model was subsequently used to investigate the wave interaction with a cylinder situated near a vertical wall. The image principle was applied to transform the original problem into an equivalent one of wave diffraction caused by two symmetrical cylinders in open seas exposed to bi-directional incident waves. The second-order wave run-up on the cylinder can then be determined using the wave elevation QTF obtained from an analysis of the equivalent problem. A detailed numerical analysis was then conducted. Numerical results revealed that the presence of the vertical wall can apparently disturb the wave diffraction process from the cylinder, and lead to significantly amplified second-order wave elevation within the region between the wall and cylinder. In addition, the respective contribution from the first- and second-order components to the overall wave elevation around the cylinder was discussed.     

航海安全水池三维造波机结构形式与水动力计算

本文重点介绍了交通部上海船舶运输科学研究所三维造波机项目研制过程中的各技术参数的确定,该造波机的特点以及结构形式的选择;对解决主要技术难点所采取的相应办法和必要的质量精度控制手段。同时,给出了进行水动力计算分析所使用的基本公式     

Variation of whitecap coverage with wave-field conditions

Field observations were carried out at a sea observation tower to investigate how whitecap coverage on the ocean surface responds to wave-field conditions. Images of whitecaps were taken for every 4 h or 7 h in the daytime using a 3CCD digital video camera fixed at 14 m elevation, and they were stored automatically in a hard disk video recorder at a time interval of 1 s. The determination of whitecap coverage was made by means of a digital image processing. The 1/3 power of whitecap coverage increases linearly with increasing the 10-m neutral wind speed. On the basis of the deflection angle between the propagating directions of wind waves and swell, wave-field conditions are classified into four cases. The present results show that whitecaps are produced most actively under the condition of the pure windsea and they tend to be suppressed by the presence of swell. It is difficult to find a certain relation between the deflection angle and whitecap coverage. Whitecap coverage also increases with the wave age in the same wind-speed conditions.     

An experimental study of wave-in-deck loading and its dependence on the properties of the topside structure

This paper concerns the largest and arguably the most threatening wave loading component experienced by a broad range of offshore structures. It arises when an incident wave crest exceeds the elevation of the underside of the deck structure, leading to direct wave-in-deck (WID) loading. The extent of this loading may be limited to the partial submergence of some of the lowermost deck beams, or could involve the large-scale inundation of the entire deck area. Either way, very large loads can arise which must be taken into account when assessing the reliability of the structure. In an earlier contribution Ma and Swan (2020) provided an extensive laboratory study exploring the variation of these loads with the properties of the incident wave. The present paper describes a second stage of this experimental study in which the variation of the WID loads with the properties of the topside structure is addressed. Specifically, it considers the porosity, position and orientation of the topside relative to the incident wave conditions, and seeks to explore both the variations in the maximum load and the loading time–history resulting from these changes.Given the highly transitory nature of a WID loading event, coupled with the fact that the problem is governed by flow conditions at, or very close to, the instantaneous water surface, the loading process is driven by an exchange of momentum from the wave crest to the topside structure. A recently developed WID load model, based on exactly these arguments (Ma and Swan 2020), is used alongside the laboratory data to provide a break-down of the load into its component parts. This provides an enhanced physical understanding of the resulting load time–history. The first part of the study is based upon an idealised generic topside structure, allowing a systematic variation in key parameters, particularly porosity. The second part addresses a realistic topside structure demonstrating the practical relevance of earlier work. Taken together, the analysis clearly establishes the importance of the topside porosity, clarifies the spatial effects associated with the evolution of a large ocean wave beneath the plan area of a structure and explains the unexpected occurrence of impact-type loading on topside structures having a high porosity. Most importantly, the paper highlights those properties of a topside structure which must be incorporated if the WID loads are to be accurately predicted.     

舰船波浪弯矩响应的频率特性

非直壁式舰船在高浪级和高航速下的弯矩响应中,除了含有低频遭遇频率成分外,还存在着一定数量的遭遇频率的倍频成分及船体各谐调的垂向总振动频率成份,它们都会对舰船波浪弯矩的非线性响应产生相应的影响。如果舰船的第一谐调垂向总振动频率正好是遭遇频率的整数倍,这时弯矩的非线性响应将达到极值。本文从模型试验及理论计算两方面分析了舰船波浪弯矩的频率特性,对船体载荷响应理论的发展及设计载荷的确定具有指导意义。     

Transient design waves for green-water loading on bulk carriers

The wave surface profiles associated with extreme relative motion between a slender stationary vessel and the adjacent wave surface are investigated for long-crested head seas. The methodology is based upon an established statistical relationship for a Gaussian random process which indi-cates that in the vicinity of an extreme event the most probable shape of the time history approaches that of the autocorrelation function. Attention is given to the relative motion at a longitudinal position which is representative of the No. 1 hatch cover location on a bulk carrier. Second-order corrections to the wave surface profiles are used to provide estimates of nonlinear relative motions. It is shown that extreme relative motion at the hatch cover location is associated with the vessel encountering a steep-fronted wave with pronounced asymmetry in the horizontal and vertical directions. In order to evaluate the exceedence probabilities, it is hypothesized that the peaks of the nonlinear relative motions are closely correlated with the peaks of an underlying linear process. The overall methodology is applied to an investigation of relative motion exceedence probabilities for vessel lengths of 250 m and 300 m over a range of survival seastates. Received: July, 1999 / Accepted: November, 1999     

Evaluation of two atmospheric models for wind–wave modelling in the NW Mediterranean

The NW Mediterranean experiences, as illustrated by the last decade, strong and rapidly varying storms with severe waves and winds. This has motivated a continuous validation of models and the efforts to improve wave and wind predictions. In this paper we use two atmospherics models, MASS (from SMC-Meteorological Office of Catalunya) and ARPEGE (from Météo-France), to force two third generation wave models: WAM and SWAN. The evaluation and comparison has been carried out for two severe storms registered in November 2001 and March–April 2002.The ARPEGE and MASS models predicted higher 10 m wind speeds than coastal meteorological stations, a fact attributed to local land influences. Regarding the 10 m wind direction, models do not present large differences, although considerable deviations from recorded data were found during some dates. ARPEGE presents less scatter and lower errors than MASS when compared with QuikSCAT data.The 10m wind fields from both atmospheric models were used to force the two selected wave models and analyse the errors and sensitivities when predicting severe wave storms. The wave model simulations show some interesting results; during the storm, the spatial wave pattern using ARPEGE showed a higher maximum, although the values of significant wave height at the buoys were lower than the ones forced by MASS (with both WAM and SWAN). The SWAN simulations show a better agreement in predicting the growing and waning of the storm peaks. The prediction of mean period was improved when using the ARPEGE wind field. However the underestimation by SWAN due to the large energy at high frequencies was evident. Validation of spectral shape predictions showed that it still has considerable error when predicting the full frequency spectra. The storms showed bimodal spectral features which were not always reproduced by wave models and are likely to be responsible for part of the discrepancies.