Hydrodynamic optimization of ship hull forms in shallow water

A computational method for improving hull form in shallow water with respect to wave resistance is presented. The method involves coupling ideas from two distinct research fields: numerical ship hydrodynamics and nonlinear programming techniques. The wave resistance is estimated by means of Morinos panel method, which is extended to free surface flow and considers the influence of finite depth on the wave resistance of ships. This is linked to the optimization procedure of the sequential quadratic programming (SQP) technique, and an optimum hull form can be obtained through a series of iterations giving some design constraints. Sinkage is an important factor in shallow water, and this method considers sinkage as a hydrodynamic design constraint. The optimization procedure developed is demonstrated by selecting a Wigley (C _B = 0.444) hull and the Series 60 (C _B = 0.60) hull, and new hull forms are obtained at Froude number 0.316. The Froude number specified corresponds to a lower than critical speed since most of the ships operating in shallow water move below their critical speed. The numerical results of the optimization procedure indicate that the optimized hull forms yields a reduction in wave resistance.     

Ship hull form optimization by evolutionary algorithm in order to diminish the drag

This study presents a numerical method for optimizing hull form in calm water with respect to total drag which contains a viscous drag and a wave drag. The ITTC 1957 model-ship correlation line was used to predict frictional drag and the corrected linearized thin-ship theory was employed to estimate the wave drag. The evolution strategy (ES) which is a member of the evolutionary algorithms (EAs) family obtains an optimum hull form by considering some design constraints. Standard Wigley hull is considered as an initial hull in optimization procedures for two test cases and new hull forms were achieved at Froude numbers 0.24, 0.316 and 0.408. In one case the ES technique was ran for the initial hull form, where the main dimensions were fixed and the only variables were the hull offsets. In the other case in addition to hull offsets, the main dimensions were considered as variables that are optimized simultaneously. The numerical results of optimization procedure demonstrate that the optimized hull forms yield a reduction in total drag.     

高速巡逻艇阻力预报及船型优化研究

为了快速、准确地获得高速船型的阻力性能,采用Michell积分法计算某高速巡逻艇的兴波阻力,并将计算结果同线性化的Rankine源法相比较,从而证实了该方法的有效性。同时以Michell积分法为基础,采用非线性规划法进行优化计算,在短时间内能获得性能优良的改良船型,由此可见,Michell积分法对于快速预报高速船型的阻力性能和船型优化是可靠的。     

保证耐波性能的目标函数的Wigley船型优化(英文)

The research performed in this paper was carried out to investigate the computational procedure to design seakeeping optimized ship hull form. To reach the optimized hull form, four stages should be done, which consists of: generate alternative hull form, seakeeping calculations, objective functions and optimization techniques. There are many parameters that may be determined in ship hull form optimization. This paper deals with developed strip theory for determining the seakeeping performance, genetic algorithm(GA) as optimization method, high order equations for curve fitting of the hull form and finally reaching to the minimum bow vertical motion in regular head waves. The Wigley hull is selected as an initial hull and carried to be optimized. Two cases are considered. For the first case, the only form coefficients of the hull(C B, C M, C W, C P) are changed and main dimensions(L, B, T) are fixed. In the second case both hull form and main dimensions are varied simultaneously. Finally, optimized hull form and its seakeeping performances are presented. The results of optimization procedure demonstrate that the optimized hull forms yield a reduction in vertical motion and acceleration.     

非线性兴波数值方法在高速三体船侧体布局方案比较中的应用

为使三体船侧体布局方案阻力性能比较更加可靠,对单体船非线性自由面边界条件的兴波阻力预报程序进行改进,成功开发了考虑升沉和纵倾影响的三体船非线性兴波阻力预报程序,对15种侧体布局方案的Wigley三体船兴波阻力进行计算,并将其与线性薄船理论计算结果、线性自由面条件的Dawson型方法计算结果、模型试验结果进行比较,表明非线性兴波阻力数值方法能够更好地反映三体船兴波阻力特性,用于三体船侧体布局优化设计时较其他2种数值方法更加可靠.     

基座结构形式对艇体振动特性的影响研究

合理设计船体基座连接结构使其能够有效阻断振动波的传递,这对双层圆柱壳结构减振降噪具有重要的工程应用价值。基于波动理论,探索了有限尺度的"L"形和""形连接结构的波动特性,分析了结构边界对振动波传递的影响规律。以某一双层圆柱壳动力舱段为例,通过数值试验对比分析了不同基座结构连接形式对双层圆柱壳振动特性的影响规律。在此基础上开展了大尺度模型的振动试验测试,为基座连接结构声学设计提供了依据。试验结果表明:""形基座连接结构具有高传递损失特性,基座连接形式改进后双壳动力舱段10-1000Hz频段振动加速度级平均降低约3dB。     

基于剪流分布规律的节点力加载方式在船体结构有限元分析中的应用

船体结构强度评估是船舶建造与设计过程中的重要环节.本文在总结研究现有的船体结构有限元分析加载方式的基础上,提出基于剪流分布规律的节点力加载方式.对于为模拟船体梁载荷而在各剖面处施加的集中力以及为进行强度计算需在各剖面处施加的调整载荷,使用本文方法将其离散至单元网格节点处并于与加载,得到的结果符合船体梁弯曲时的应力分布规律,这对于正确进行船体结构强度评估具有重要意义.给出适用于计算机实施的规格化加载过程,以实现船体结构有限元分析的自动加载过程.     

改进Sobol’方法在船型优化模型中的应用

针对船型优化中采用更多的优化变量有可能带来"维度灾难"的问题,通过灵敏度分析确定不重要的变量并降维来缓解该问题。介绍以往提出的改进Sobol’方法,利用该方法对某集装箱船兴波阻力优化模型进行灵敏度分析并降维。为减少分析的计算量,对该船型优化模型构建Kriging模型。对优化模型降维前后的优化过程、最优解及其波形和型线进行对比。结果表明:降维后优化模型收敛更快,最优解兴波阻力系数仅增大0.15%,采用改进Sobol’方法进行降维,能在保证最优解质量的同时,提高优化效率。     

Resistance analysis of a semi-SWATH design concept in shallow water

Resistance analysis is an important analytical method used to evaluate the hydrodynamic performance of High Speed Craft (HSC). Analysis of multihull resistance in shallow water is essential to the performance evaluation of any type of HSC. Ships operating in shallow water experience increases in resistance because of changes in pressure distribution and wave pattern. In this paper, the shallow water performance of an HSC design concept, the semi-Small Waterplane Area Twin Hull (semi-SWATH) form, is studied. The hull is installed with fin stabilizers to reduce dynamic motion effects, and the resistance components of the hull, hull trim condition, and maximum wave amplitude around the hull are determined via calm water resistance tests in shallow water. These criteria are important in analyzing semi-SWATH resistance in shallow water and its relation to flow around hull. The fore fin angle is fixed to zero degrees, while the aft fin angle is varied to 0°, 5°, 10°, and 15°. For each configuration, investigations are conducted with depth Froude numbers (Fr _H ) ranging from 0.65 to 1.2, and the resistance tests are performed in shallow water at the towing tank of UTM. Analysis results indicate that the resistance, wave pattern, and trim of the semi-SWATH hull form are affected by the fin angle. The resistance is amplified whereas the trim and sinkage are reduced as the fin angle increases. Increases in fin angle contribute to seakeeping and stability but affect the hull resistance of HSCs.     

Hydrodynamic hull form optimization using parametric models

Hydrodynamic optimizations of ship hull forms have been carried out employing parametric curves generated by fairness-optimized B-Spline form parameter curves, labeled as F-Spline. Two functionalities of the parametric geometry models are used in the present study: a constrained transformation function to account for hull form variations and a geometric entity used in full parametric hull form design. The present F-Spline based optimization procedure is applied to two distinct hydrodynamic hull form optimizations: the global shape optimization of an ultra-large container ship and the forebody hull form for the hydrodynamic optimization of an LPG carrier. Improvements of ship performance achieved by the proposed F-Spline procedure are demonstrated through numerical experiments and through correlations with experimental data. The ultra-large containership was built and delivered to the ship owner. The present study validates the effectiveness of the proposed hydrodynamic optimization procedure, ushering in process automation and performance improvement in practical ship design practices.     

超细长三体船阻力计算研究

主船体为超细长体,两侧配置两个小侧体而形成的三体船是一种很有潜力的新船型,近年来已引起了广泛的关注。本文对三体船的阻力原理进行了分析,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;采用线性兴波阻力理论建立三体船的兴波阻力计算方法,提出了一套计算三体船阻力的完整方法。经与船模试验结果比较,采用本方法预报三体船的阻力,Cw的计算结果可以定性地反映侧体布置位置对三体船兴波阻力的影响,计算结果比较接近实际情况,具有一定的可靠性,可用于该船型的阻力预报。     

基于集成仿真的灯光渔船艏部型线优化

针对我国现有渔船标准化建设中遇到的船体型线优化难的问题,提出一种基于集成仿真优化技术的船体型线优化方法,并以一艘灯光渔船的兴波阻力性能优化为例,通过半参数化方法提取10个控制参数用于艏部型线的变换,兴波阻力采用势流理论方法进行评估,并采用Sobol算法与梯度搜索算法相结合的优化算法。基于上述的船体型线优化方法最终得到兴波阻力性能最优的船型,优化结果表明,文中提出的船体优化技术是有效的,有助于加快推进渔船船型的标准化建设。     

考虑定常兴波影响的辐射问题去奇Rankine源方法数值计算

随着中高速船舶在海洋资源开发中的广泛应用,航速对船舶在波浪中摇荡运动的影响受到重视。本文基于势流理论,采用非均匀有理B样条(NURBS)表达物面,应用去奇Rankine源方法求解流场速度势;推导了兴波问题的二阶近似非线性自由面边界条件,以及考虑二阶近似非线性兴波影响的辐射速度势的线性自由面和物面边界条件。本文编程首先数值计算了Wigley船型的近似非线性兴波问题,将计算的线性和非线性兴波阻力系数与文献结果做了比较;然后数值计算了计及线性定常兴波影响的下潜圆球有航速辐射问题,将计算的附加质量和阻尼系数与文献结果比较。本文计算结果与文献结果吻合程度较好,验证了本文数值计算方法的有效性。文中还给出了兴波波形和辐射波形。     

水下爆炸冲击波与气泡载荷作用下船体结构的动响应

由冲击波引起的结构动力毁伤与由气泡引起的结构动力毁伤机理不同.基于双渐近（DAA）理论,建立-套有限元方法与边界元方法相结合的数值计算程序.分别研究非接触水下爆炸冲击波载荷与气泡载荷作用下三维船体结构的动响应,阐述水下爆炸载荷与三维船体结构之间的流固耦合理论.通过算例,详细讨论冲击波与气泡载荷作用下船体结构的总体响应和局部响应的-些特征与机理.计算结果表明,在非接触水下爆炸中,冲击波主要是对船体结构造成局部毁伤,而气泡则会对船体结构造成总体与局部的双重毁伤.     

我国浮式生产储油装置技术的发展现状

介绍了我国浮式生产储油装置（FPSO）的分布现状,描述了我国渤海与南海不同海域FPSO的特点。为了使FPSO长期系泊在海上安全生产、运营可靠,从FPSO设计关键,诸如船体波浪载荷、油气工艺模块支架与船体连接技术、不同单点系泊系统的船体结构设计等方面进行了重点阐述。     

浅水中半小水线面双体船概念设计的阻力分析（英文）

Resistance analysis is an important analytical method used to evaluate the hydrodynamic performance of High Speed Craft(HSC). Analysis of multihull resistance in shallow water is essential to the performance evaluation of any type of HSC. Ships operating in shallow water experience increases in resistance because of changes in pressure distribution and wave pattern. In this paper, the shallow water performance of an HSC design concept, the semi-Small Waterplane Area Twin Hull(semi-SWATH) form, is studied. The hull is installed with fin stabilizers to reduce dynamic motion effects, and the resistance components of the hull, hull trim condition, and maximum wave amplitude around the hull are determined via calm water resistance tests in shallow water. These criteria are important in analyzing semi-SWATH resistance in shallow water and its relation to flow around hull. The fore fin angle is fixed to zero degrees, while the aft fin angle is varied to 0o, 5o, 10o, and 15o. For each configuration, investigations are conducted with depth Froude numbers(Fr H) ranging from 0.65 to 1.2, and the resistance tests are performed in shallow water at the towing tank of UTM. Analysis results indicate that the resistance, wave pattern, and trim of the semi-SWATH hull form are affected by the fin angle. The resistance is amplified whereas the trim and sinkage are reduced as the fin angle increases. Increases in fin angle contribute to seakeeping and stability but affect the hull resistance of HSCs.     

双体船/三体船兴波阻力数值预报方法研究

采用改进的Dawson方法,自行开发了可用于双体船、三体船兴波阻力的数值预报程序,并且考虑了高速三体船方尾的处理.利用本文的数值预报方法分别计算了一条小水线面双体船和一条三体船,验证了本文的数值预报方法在一定范围内能较合理地预报双体船、三体船的兴波阻力.此外,还讨论了该方法在三体船片体位置优化中的应用,通过和试验值对比验证了该方法可用于三体船片体布局优化.     

Review of the uncertainties associated to hull girder hydroelastic response and wave load predictions

This paper reviews the importance of uncertainties in hull girder loads influenced by flexible fluid structure interactions. The focus is on developments in the field of hydroelastic modelling, simulation and model tests of practical relevance to the prediction hull girder wave load predictions and their validation. It is concluded that whereas hydroelastic methods for use in design development and assessment become increasingly useful, challenges in realizing and modelling uncertainties can be attributed to: (1) the limitations of numerical methods to suitably model nonlinearities; (2) the ambiguity of model tests; and (3) the systematic use of data emerging from computational, model- or full-scale methods. An approach is recommended to assess the uncertainty in the hydroelastic responses to wave loading and an example is provided to demonstrate the application of the procedure.     

不同航速下船体波浪诱导运动和载荷计算研究

应用三维时域水动力理论,以挪威船级社（DNV）的WASIM程序系统作为主要工具,分析研究了一条在国际航线上航行的某一集装箱船的水动力特性,包括船体运动与波浪诱导载荷的规律,给出了不同航速下的船体运动特性和剖面诱导载荷百年一遇长期预报结果,深入分析了船体的航速效应,为船体设计中船体波浪载荷设计提供了参考依据。     

CAE在船舶性能研究领域的应用

论述了计算机辅助工程(Computer Aided Engineering,简称CAE)技术的重要性及其在船舶性能领域应用的可行性。从原理、特点、功能、构成、应用效果及未来发展诸方面介绍了中国船舶科学研究中心在CAE技术领域自主创新的技术成果和在研项目,其中包括船型设计系统、水动力性能预报系统、数字水池试验系统、数值水池仿真系统和船舶技术性能数据库等五大系统。上述诸系统既相互独立,又有机联系,共同构成船舶性能研究的综合系统。