兴波阻力数值预报方法研究及其在集装箱船船型优化中的应用

集装箱船作为一种中高速船,其兴波阻力在总阻力中所占比例较高。从某种意义上讲,船型优化就是寻求最小兴波阻力的船型。本文采用基于势流理论的面元法预报集装箱船的兴波阻力,对两种计算兴波阻力的方法进行了研究比较：第一种是改进的Dawson方法,传统的Dawson方法采用静水面上的叠模流线网格,而改进的Dawson方法是采用静水面上的贴体网格来计算兴波阻力;第二种方法是单模流动法。文中利用这两种方法计算了两条集装箱船,通过和试验值比较,发现这两种方法在设计航速附近的一定范围内都能正确地识别船型变化对兴波阻力的影响,验证了这两种数值预报方法都可以用于船型优化。但是改进的Dawson方法的计算结果更接近实验值,因此改进的Dawson方法更适用于船型优化。     

自由面区域变换法解三体船兴波问题

为求解三体船兴波问题,基于线性自由面条件的势流兴波理论Rankine源方法,利用物理平面与计算平面的转换关系计算自由面上物理量的导数,开发了三体船兴波阻力预报程序.采用该方法和程序,对不同侧体布局的Wigley三体船兴波阻力及波形进行计算,并将计算结果与模型试验结果、其他作者数值计算结果进行比较,验证了该方法对三体船的适用性,表明采用贴水线网格及自由面区域变换法解三体船兴波问题可提高三体船兴波问题求解效率.     

An iterative Rankine boundary element method for wave diffraction of a ship with forward speed

A 3-D time-domain seakeeping analysis tool has been newly developed by using a higher-order boundary element method with the Rankine source as the kernel function. An iterative time-marching scheme for updating both kinematic and dynamic free-surface boundary conditions is adopted for achieving numerical accuracy and stability. A rectangular computational domain moving with the mean speed of ship is introduced. A damping beach at the outer portion of the truncated free surface is installed for satisfying the radiation condition. After numerical convergence checked, the diffraction unsteady problem of a Wigley hull traveling with a constant forward speed in waves is studied. Extensive results including wave exciting forces, wave patterns and pressure distributions on the hull are presented to validate the efficiency and accuracy of the proposed 3-D time-domain iterative Rankine BEM approach. Computed results are compared to be in good agreement with the corresponding experimental data and other published numerical solutions.     

最小阻力船型优化研究

本文基于线性兴波阻力理论，把控制尾流分离作为约束条件，利用优化计算方法对设计水线下船体外形进行优化研究。以数学船型Ｗｉｇｌｅｙ船型为母型进行了计算，分别讨论了最小兴波阻力船型和最小总阻力船型的确定方法，并将所得到的改良船型进行了船模阻力试验，结果证实了本优化设计方法的可靠性。     

An iterative Rankine BEM for wave-making analysis of submerged and surface- piercing bodies in finite water depth

A 3-D iterative Rankine Boundary Element Method （BEM） for seakeeping problem in time domain is developed in the framework of linear potential theory. Waves generated by both submerged and surface-piercing bodies moving at a constant forward speed in otherwise calm water, and the resultant steady wave pattern, wave profile and resistance are computed to validate this newly-developed code. A rectangular computational domain moving with the same forward speed as the body is introduced, in which an artificial damping beach is installed at an outer portion of the free surface except the downstream side for satisfying the radiation condition. The velocity potential on the ship hull and the normal velocity on the free surface are obtained directly by solving the boundary integral equation, with the Rankine source used as the kernel function. An iterative time-marching scheme is employed for updating both kinematic and dynamic free surface boundary conditions to stabilize the calculation. Extensive results including the wave patterns, wave profiles and wave resistances for a submerged spheroid and a Wigley hull with forward speed are presented to validate the efficiency of the proposed 3-D time-domain higher-order approach. Finally, the sensitivity of ship-generated waves to the water depth is investigated. Computed results show satisfactory agreement with the corresponding experimental data and other numerical solutions.     

OPTIMIZATION OF A WAVE CANCELLATION MULTIHULL SHIP USING CFD TOOLS

1. INTRODUCTIONA smallwaterplane area, trihull ship, termed the wave cancellation multihull ship (or trimaran), offers the possibility of dramatic wave drag reduction due to wave cancellation. Experimental evidence, e.g. by Wilson et al. (1993) indi…     

Ship hull optimization based on wave resistance using wavelet method

The ship hull surface optimization based on the wave resistance is an important issue in the ship engineering industry. The wavelet method may provide a convenient tool for the surface hull optimization. As a preliminary study, we use the wavelet method to optimize the hull surface based on the Michel wave resistance for a Wigley model in this paper. Firstly, we express the model's surface by the wavelet decomposition expressions and obtain a reconstructed surface and then validate its accuracy. Secondly, we rewrite the Michel wave resistance formula in the wavelet bases, resulting in a simple formula containing only the ship hull surface's wavelet coefficients. Thirdly, we take these wavelet coefficients as optimization variables, and analyze the main wave resistance distribution in terms of scales and locations, to reduce the number of optimization variables. Finally, we obtain the optimal hull surface of the Wigley model through genetic algorithms, reducing the wave resistance almost by a half. It is shown that the wavelet method may provide a new approach for the hull optimization.     

WAVE MAKING COMPUTATION IN TIME DOMAIN FOR MULTI-HULL SHIPS

1. INTRODUCTION For high-speed displacement ships, the wave making at the free surface is an important hydro- dynamic performance. The wave making reduction has attracted more attention for ship designers. The ship wave resistance and ship hull form improvement have been widely investigated. The thin ship theory adopting the Havelock source distribution on the ship centerline plane can be used to analyze the ship wave making profile and the ship wave resistance may be obtained by ship wav…     

Hull form optimization of a cargo ship for reduced drag

Hydrodynamic optimization of the hull forms can be realized through the implementation and integration of computational tools that consist of a hydrodynamic module, a hull surface representation and modification module, and an optimization module. In the present paper, a new bulbous bow generation and modification technique has been developed and integrated into the hull surface representation and modification module. A radial basis function based surrogate model is developed to approximate the objective functions and reduce the computing cost. A multi-objective artificial bee colony optimization algorithm is implemented and integrated into the optimization module. To illustrate the integrated hydrodynamic optimization tools, a cargo ship is optimized for reduced drag. The optimal hull forms obtained are then validated computationally and experimentally. Validation results show that the present tools can be used efficiently and effectively in the simulation based design of the hull forms for reduced drag.     

COMPUTATIONAL RESEARCH ON WAVE MAKING OF MOVING WIGLEY HULL IN TIME DOMAIN

Based on Green＇s theorem, a time domain numerical model was constructed to simulate wave making phenomenon caused by a moving ship. In this article, the Rankine sources and dipoles were placed on boundary surfaces （i.e., the ship surface and free surface）, and a time-stepping scheme was employed. Its unique characteristic is that steady state can be realized from initial value by employing the time-stepping scheme and unsteady free surface conditions. In time domain, if the results of unsteady flow problem tend to data stabilization after many time steps of computation, they could be regarded as the data of steady ones. This model could be employed to steady or unsteady problems. Theoretical reasoning and computational process of this method was described in detail The linear and nonlinear boundary conditions on body surface were studied, and the relative means to realize these boundary conditions in iterative computation were also discussed. Some proper parameters about the model of the Wigley hull were determined by many numerical tests, and their influences on wave making resistance and wave pattern were discussed. According to the comparison between numerical results and data available in relative references, the method used in this work is proven to be a reliable method in time domain. And the lattice reorganization in every time step computation is a feasible numerical approach.     

An overview of simulation-based hydrodynamic design of ship hull forms

This review paper presents an overview of simulation-based hydrodynamic design optimization of ship hull forms. A computational tool that is aimed to accomplishing early-stage simulation-based design in terms of hydrodynamic performance is discussed in detail. The main components of this computational tool consist of a hydrodynamic module, a hull surface modeling module, and an optimization module. The hydrodynamic module includes both design-oriented simple CFD tools and high-fidelity CFD tools. These integrated CFD tools are used for evaluating hydrodynamic performances at different design stages. The hull surface modeling module includes various techniques for ship hull surface representation and modification. This module is used to automatically produce hull forms or modify existing hull forms in terms of hydrodynamic performance and design constraints. The optimization module includes various optimization algorithms and surrogate models, which are used to determine optimal designs in terms of given hydrodynamic performance. As an illustration of the computational tool, a Series 60 hull is optimized for reduced drag using three different modification strategies to outline the specific procedure for conducting simulation-based hydrodynamic design of ship hull forms using the present tool. Numerical results show that the present tool is well suited for the hull form design optimization at early design stage because it can produce effective optimal designs within a short period of time.     

水面舰船加装减阻节能球鼻艏研究

该文基于波形叠加的消波原理,对一艘仿阿雷.伯克级大型驱逐舰加装减阻节能球鼻艏进行研究,研究表明大型驱逐舰加装减阻节能球鼻艏可获得较好的减阻效果。文中首先给出了基于细分曲面表达船型,采用船体曲面法向量分量表示源强的船舶兴波阻力及波形计算的数值方法,通过与实验结果的比较,分析了该方法的合理性和有效性;在此基础上通过逆向设计法优化计算和分析得到了一仿阿雷.伯克级大型驱逐舰船型加装减阻节能球鼻艏消波减阻定性规律和定量效果,在特定的中高航速下通过减阻节能球鼻艏优化设计可以使兴波阻力最多减少33.7%。     

三体船船型分析及兴波干扰的模型试验研究

以本文设计的高速三体船型线为研究对象,分析了三体船船型的特点。应用均匀设计法进行了三体船兴波干扰的模型试验研究,依据试验结果分析了片体位置对三体船兴波干扰的影响,比较了同用途三体船与单体船的阻力性能,并讨论了多体船快速性试验结果的换算问题。     

基于遗传算法与NM理论的船型优化

阻力性能的优化一直是船舶设计工作的重要环节,它将直接决定船舶的经济性和适用性。该文利用基于Neumann-Michell(NM)势流理论自主开发的船舶兴波阻力计算求解器NMShip-SJTU和遗传算法(genetic algorithm,GA),对标准船型Series 60进行船型优化分析。利用平移法(Shifting Method)与径向基函数法(radial basis function method,RBF)修改船体曲面,开发了一套包含优化算法、船型变换模块在内的全自动船型优化程序(OPTShip-SJTU),并应用。高航速(Fr=0.30)下的Series 60船型的优化,得到能使兴波阻力有效减小的优化船型。     

RESEARCH ON THE METHOD AND CALCULATION OF THE NEW SLENDER-SHIP WAVE RESISTANCE THEORY

BRIEFINTRODUCTIONOFTHEPAPER :　InChapter 1,anoverviewmainresearchactivitiesaboutwaveresistancesincethefamouspioneeringstudyofMichellin 1898aregiven .InChapter 2 ,Noblesse’snewslender shiptheoryofwaveresistanceisinvestigatedindetail.InChapter 3,calculationformulasofzeroth first andsecond orderwaveresistancearederivedandcorrespondingcalculation programsarecom piled .InthesingleanddoubleintegralpartsofGreen’sfunction ,thekernelfunctionofwave makingresistanceexpression ,specialfunct…     

STUDY OF TRIMARAN WAVEMAKING RESISTANCE WITH NUMERICAL CALCULATION AND EXPERIMENTS

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FULLY NONLINEAR WAVE COMPUTATIONS FOR ARBITRARY FLOATING BODIES USING THE DELTA METHOD

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Practical evaluation of the drag of a ship for design and optimization

We consider two major components of the drag of a ship, the“friction drag”and the“wave drag”, that are related to vis-cous friction at the hull surface and wavemaking, and mostly depend on the Reynolds...     

基于CFD方法的船/桨/舵干扰数值模拟

船/桨/舵相互干扰研究在传统船型优化设计和新船型的开发中具有重要意义。应用计算流体力学(CFD)方法对带桨的KCS集装箱船及带桨和舵的KVLCC2油船非稳态粘流场进行了数值模拟,其中船桨舵干扰计算分别采用动量源法、MRF法和滑移网格法,分析研究了各方法及其结果的异同。研究表明不同模拟计算方法均能合理预报出船/桨/舵相互干扰相互作用下速度场和压力场分布等详细流场信息,可用于计算船体阻力、表面压力和桨盘面伴流等。通过这种详细的数值模拟研究,可以更好地理解复杂流动干扰现象。     

NUMERICAL RESEARCH ON UNSTEADY SHIP WAVE-MAKING PROBLEMS IN TIME-DOMAIN

A time-domain Kelvin source high-order panel method based on NURBS is developed and applied to solve the unsteady wave-making problems. Numerical results of instant wave resistance and free surface elevation are presented and compared with the availaby results by other authors, for submerged spheroid and sphere beneath the free surface and for surface ship of Wigley models moving with unsteady speed,The agreement is satisfying.