分段式尾压浪板对高速船阻力性能的影响

基于CFD技术,以排水型高速船Model 5b为模型,寻求改善高速船阻力性能的尾压浪板新形式。首先尾压浪板新形式的确定在静水条件下进行,然后在波浪条件下验证该压浪板的阻力性能。基于CFD软件建立三维数值波浪水池,静水条件下采用切割体网格技术预报船模的阻力性能。波浪条件下数值水池入口采用直接造波方法,尾部采用人工阻尼消波方法,自由面采用VOF方法处理,采用重叠网格技术预报船模的阻力性能以及运动响应。确定一种比常规压浪板阻力性能优良的分段式压浪板,为船舶节能附体的研究提供参考。     

Solution of an unstable inverse problem: wave source evaluation from observation of velocity distribution

This paper illustrates how to estimate a wave source generating a wave system, including local waves, with the assumption of linear dispersive waves of two dimensions. The estimation of wave source is realized by using an inverse problem. Unfortunately, the inverse problem is ill-posed in the sense of stability, since the wave source information included in local waves diminishes as the distance from the wave source increases. In the area of applied mathematics, there are well-developed methods to tackle ill-posed problems, which are called regularizations. In this paper, three different regularizations which are well known in applied mathematics are introduced and investigated to learn whether they are applicable to the present problem of the estimation of wave source. From the numerical experiments, it is shown that the estimation is realized by the regularizations introduced in this study, so that they can be applied to the determination of a wave source generating a wave system including local waves. Received: June 6, 2000 / Accepted: February 7, 2001     

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。     

顶浪、斜浪中复合材料双体艇艇体结构耦合响应数值分析

采用流固耦合（Fluid-Structure Interaction,FSI）的艇体波浪载荷和结构响应的数值分析方法,对顶浪、斜浪中复合材料双体艇结构的动态响应进行研究。分别建立了完整的复合材料艇体有限元模型以及流场模型,基于数值水池造波技术,通过计算获得了顶浪、斜浪中复合材料艇体结构的时域动态响应结果,选取高应力梯度区域,通过网格加密重构同时获得了复合材料的层间应力。选取具有代表性的前10大等效应力与内外面板最值主应力,在将 FSI与传统基于经验公式的有限元法（Finite Element Method,FEM）的结果对比中发现,FSI中拱、中垂的计算结果更接近于 FEM弯扭组合工况,而采用《钢制双体船直接计算指南》计算复合材料双体艇时,所用经验公式的顶浪航行波浪载荷计算值偏小。     

栾家口和蓬莱东港区波浪特性与掩护水域波况研究

根据龙口、蓬莱海洋站实测波浪资料,分析烟台港栾家口港区和蓬莱东港区的波浪特性,结果显示该海区属于以风浪为主、涌浪为辅的混合浪。利用TK-2D的PEM波浪数学模型模拟工程前波浪,得到工程区设计波要素,栾家口港区的强浪向是偏WNW向,蓬莱东港区的强浪向是偏NE向。利用MIKE21的BW方程波浪数学模型对平面布置方案下港内的波况进行模拟。在掩护水域由于采用直立式码头,波浪发生多次反射,码头前波高较大,为减小港内波高,对方案进行优化,采用高桩等反射率小的码头结构型式,可以消散港内波能,有效减小码头前波高。     

Open boundary conditions in stratified ocean models

In most applications of numerical ocean models, artificial boundaries are introduced to limit the domain. Along such a boundary we need to apply what is often referred to as an open boundary condition (OBC). In this paper a number of local methods used in barotropic ocean models are applied and discussed for the stratified case using a normal mode approach. The OBCs are the simple conditions: clamped, prescribed and zero gradient; the radiation conditions: Camerlengo–O'Brien, Orlanski and a method of characteristics based on linear equations; and a sponge type condition: the flow relaxation scheme. The OBCs have been implemented in a 3-layer ocean model and examples of how the various OBCs perform for three simple flow situations are investigated. The cases are: internal wave radiation, a quasi-steady coastal jet and the response to a storm moving across a strait. It is found that the flow relaxation scheme and the method based on characteristics perform well for the test cases in general, although some of the simpler methods give better results in individual cases.     

A time-domain higher-order boundary element method for 3D forward-speed radiation and diffraction problems

A time-domain higher-order boundary element method for seakeeping analyses in the framework of linear potential theory is newly developed. Ship waves generated by two modified Wigley models advancing at a constant forward speed in calm water or incident waves and the resultant radiation and diffraction forces are computed to validate this code. A rectangular computational domain moving with the same forward speed as the ship 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 calculated directly by solving the boundary integral equation. An explicit time-marching scheme is employed for updating both kinematic and dynamic free-surface boundary conditions, with an embedding of a second-order upwind difference scheme for the derivative in the x-direction to stabilize the calculation. Extensive results including the exciting forces, added mass and damping coefficients, wave profiles, and wave patterns for blunt Wigley and slender Wigley hulls with forward speed are presented to validate the efficiency of the proposed 3D time-domain approach. The corresponding physical tests of the radiation and diffraction problems in a towing tank are also carried out. Computed numerical results show good agreement with the corresponding experimental data and other numerical solutions.     

斜坡型潜导堤波浪力特性的数值研究

为研究各水位期不同波高作用条件下,斜坡型潜堤所受波浪力的特性,基于某潜导堤工程设计与物理模型资料,采用FLUENT软件建立二维波浪数值水槽,用物理模型试验数据验证模型的可靠性,对不同淹没水深和波高下斜坡型潜导堤所受波浪力进行数值计算,分析波浪力与相对波高、相对淹没水深之间的关系,结合其他形式潜堤波浪力的经验计算公式拟合得出该斜坡型潜导堤堤顶面最大波浪力计算公式。结果表明:波浪力大小受相对波高、相对淹没水深的影响较为显著,其影响机理与波浪场流体运动特征相关;相对于波高的变化,波浪力对淹没水深的变化更为敏感,且波浪力在不同的淹没水深区间和不同的作用位置均呈现出不同的变化规律。     

On the realization of nonlinear wave profiles using the Banach fixed-point theorem: Stokes wave in a finite depth

A new mathematical formulation for the realization of nonlinear wave profiles and its nonlinear solution procedure, based on the Banach fixed-point theorem, is proposed. To apply the formulation, a nonlinear equation for the Stokes wave in a finite depth was derived, and some numerical solutions are given. A numerical study showed that the proposed iteration method, based on linear progressive wave potential only, enabled us to realize the Stokes nonlinear wave profiles in a finite depth. The nonlinear strategy of iteration has a very fast convergence rate, i.e., only about 6–10 iterations are required to obtain a numerically converged solution.     

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。     

大型港区港内波浪条件分析研究

以某大型港区工程为实例,通过波浪整体物理模型试验,研究了通过防波堤口门传入港区的波浪条件,并采用数学模型模拟了港内局部小风区成浪的影响。并将两者的结果按照相关方法进行了合成和对比分析。结果表明,对于大型港区,港内局部小风区风成浪对港内码头设计波浪要素和码头泊稳条件都有一定的影响,这是大型港区设计时需要考虑的因素。同时还指出对于防波堤越浪的情况,应考虑越浪产生的堤后次生波对港内码头处波浪条件的影响。     

基于数值和实验方法的非透浪梳式防波堤的水动力学特性研究

采用源函数造波法建立了三维数值波浪水槽模型,模拟了不同随机种子数(NW)下的随机波浪,与目标谱对比的结果证明当NW=200时,采用文中的数值方法可以得到较好的模拟精度;建立了随机波浪对一种非透浪梳式防波堤作用的数值模型,通过数值模拟结果和实验结果的比较,验证了该数值模型的有效性。对该非透浪的梳式防波堤的水力学特性进行了实验研究,并应用上述数值方法对结构的所受冲击波浪力机理进行了分析,数值结果证明在该结构的危险水位下,由结构的翼板和胸墙下底板所构成的异型空腔结构是导致翼板上产生较大冲击压力的主要因素。在此基础上,为了消减翼板的冲击压力,提出一种改进的结构型式,最后对该改进结构的翼板上波浪力特性和波浪反射系数进行了实验研究。     

直墙式建筑物上立波作用力计算的讨论

采用Fourier近似立波数值解计算直墙式建筑物上的立波作用力,以典型波浪条件的计算结果为例,比较了数值解和我国以及日本现行规范计算方法的差异,指出了两种规范中有待进一步改进之处。     

人工航道对波浪传播规律的影响

波浪在传播过程中,遇到建筑物和地形变化时,会发生绕射与折射,对波浪的传播、变形具有显著的影响。作者建立了基于Boussinesq方程的波浪数学模型。采用所建立的数学模型对双突堤条件下有、无航道时港内的波浪分布分别进行了数值计算,并将上述两种条件下的波浪分布情况进行了比较。结果表明,开挖航道对波浪的传播变形影响较大,不能用纯绕射来代替波浪的折、绕射联合作用。     

透浪建筑物掩护水域波浪数值模拟研究

为了研究透浪水工结构掩护水域的波浪条件,采用MIKE21系列软件的BW模块及SWAN模型对假定工况下的波 浪传播进行了模拟。通过2组数值模拟结果与整体波浪物理模型试验结果的对比,比较了2种数值方法模拟掩护水域波浪条 件的可行性及适用性,然后采用SWAN模型模拟了12级风条件下潜堤掩护水域的风浪场,取得了较好的效果。     

改善进港航道引起港内波能聚集问题的研究

进港航道在口门引起波能聚集,对港内泊稳条件产生不利影响,采用适当工程措施可使该情况有所改善。文中结合某工程实例探讨了包括增加防波堤、清除浅滩和调整航道轴线的三种工程方案,并通过基于Boussinesq方程的波浪数学模型进行了对比试验,结果表明各方案均能达到缓解波能聚集、改善泊稳条件的目的,但改善效果存在一定差异。最后还对试验中采用单方向和多方向波的结果进行了初步对比探讨,对于航道波能聚集影响港内波况的问题,采用单方向不规则波的试验结果将偏于危险。     

Nonlinear wave forces on large-scale submerged tunnel element

This paper presents parametric studies of nonlinear wave forces on large-scale submerged tunnel element. A transportation project of submerged tunnel element under irregular wave conditions is taken as the research background. Three-dimensional diffraction potential and radiation potential associating with the motion of the floating body are utilized, and an efficient three dimensional Green function is implemented to solve the radiation-diffraction problem. A computational method for calculating the nonlinear wave forces of the submerged tunnel element is developed. The present method is validated by the existed methods and experimental data, and good agreements are observed for all test models. The effects of wave parameters and structural parameters on the second-order nonlinear wave forces are studied. Results from the present study can provide valuable recommendations for the weather window and downtime frequencies, the configuration of tugboats, the arrangement of sea-route, and the size and type of the design and construction of the submerged tunnel element.     

港湾内非线性波浪对船剖面作用的时域计算模型(英文)

文中用边界元数值求解复速度势模拟了波浪对船剖面的时域作用力,采用满足运动学和动力学条件的半拉朗格朗日法跟踪流体的自由表面.推导了适用本数值模型的辐射边界条件,此边界条件和海绵层边界条件组成的出口边界条件,可以使波浪很好地被吸收或传播出去.进行了相关物理模型实验,数值计算结果和实验结果的对比表明此模型能精确模拟波浪对船的作用力.     

船体艏部水动力性能优化

提出一种以势流兴波阻力理论Rankine源方法为基础,结合SHIPFLOW软件为计算工具,利用CAD-CFD集成平台FRIENDSHIP-Framework软件进行变形优化,研究船舶的最小兴波阻力型线优化设计的方法,并考察了兴波优化得到的船型总阻力变化情况。在型线优化过程中,以兴波阻力系数为目标函数,排水量变化范围为约束条件,在Wigley船体前端增加一个利用Feature建模技术参数化生成的球艏并调整艏部型线使得船体表面光顺。选取球鼻艏形状的各项参数作为基本设计变量,利用DOE方法对船艏进行优化,获得了设计航速下兴波阻力较小的船型,验证了所提方法进行船艏型线优化的有效性。相应的考察变形及优化前后总阻力变化情况表明:在高傅汝德数情况下增加球艏所带来的粘性阻力的增加小于兴波阻力的减小量,总阻力得到了改善,优化后得到的球艏能在进一步减小兴波的同时减小总阻力。此外,还运用所提方法对3100TEU船型的船艏,利用Delta Shift方法进行变形,在设计航速下,将变形的参数作为设计变量,利用DOE方法进行优化设计。结果显示:在排水量限制范围内当球鼻艏向上向前伸展一定长度时可以降低兴波阻力。与此同时,由于优化前后船体湿表面积变化很小,粘性阻力的变化并不明显,兴波的减小则使得总阻力得到了改善。