基于B样条的船体网格划分及水动力计算

基于B样条理论的特点,提出一种高效的船体水动力网格划分方法,开发相应的程序。将此方法直接应用于某50万t矿砂船的三维线性频域水动力计算中,将计算结果与文献结果进行对比分析,其结果与相关文献结果非常吻合,认为用B样条方法进行船体水动力网格划分是可行。     

规则波中船舶波浪增阻理论和经验法预报分析与比较

针对规则波中迎浪下有航速集装箱船船型阻力增加预报,采用一种改进的三维移动脉动源面元法求解船舶运动,进而通过理论方法求解辐射和绕射增阻.速度势求解引入了格林函数空间线段积分和面元积分方法,辐射增阻采用三维辐射能量法计算,绕射增阻通过二阶波浪力中绕射速度势获得.通过与试验数据对比证明了该理论预报模型在精度和效率方面有明显优势.在此预报结果基础上对经验预报模型提出了改进公式,计算结果表明了改进模型对工程设计具有较好的适用性.     

Predicting parametric rolling in irregular head seas with added resistance taken into account

Parametric rolling in irregular head seas is investigated using numerical simulation in the time domain in this paper. The effect of the change in speed due to added resistance on parametric rolling is taken into account. Three methods of calculating the added resistance in irregular head seas are applied to this problem, and then Pinkster’s method, which considers the time-varying added resistance in irregular head seas, is extended for further investigations in this paper. Furthermore, the Froude–Krylov component of restoring variation is estimated with coupling from heave and pitch motions, and the hydrodynamic effects are extrapolated nonlinearly with regards to roll angle. Finally, the “practical non-ergodicity” of parametric roll is investigated with a model experiment at zero forward speed and using the simulation, and the effect of added resistance is investigated with the simulation.     

Theoretical study on the effect of parametric rolling on added resistance in regular head seas

A formula based on Maruo’s theory is presented for the added resistance in regular head seas when parametric rolling occurs. Firstly, the velocity potential of the radiation waves due to parametric rolling, sway and yaw motions should be superposed on the conventional velocity potential. Secondly, the added resistance is averaged within the time duration that is double the encounter period. Thirdly, the stationary-phase method which is used in Maruo’s method is also used to obtain the formula of added resistance in waves with parametric rolling taken into account as well as viscous roll damping. Fourthly, source distribution based on Maruo and Ishii's and Maruo and Iwase’s works is used to calculate the added resistance. Finally, the effect of parametric rolling on added resistance in regular head seas mainly results from viscous roll damping and it becomes larger as the amplitude of parametric rolling becomes larger.     

深水SPAR风机系统全耦合动力响应分析研究

文章采用联合开发的计算程序对深水SPAR风机的浮体、锚泊和风机各子系统进行了水—气动力的全耦合数值分析,研究了深水浮式风机系统的动力响应特点。浮体水动力计算采用基于二阶精度的混合波浪模型(Hybrid Wave Model)的MORISON公式,锚泊系统采用细长杆理论通过非线性有限元方法实现,风机系统的空气动力分析采用基于多体气动弹性理论的FAST模块。以浮体控制方程为主体,通过模块间的载荷与位移传递在每个时间步上迭代求解,形成完全耦合的时域分析方法。通过对NREL的5MW SPAR风机系统在随机海况下的水动力响应分析,验证了该方法的有效性,并分析了浮式风机子系统间的混合动力作用。     

Fully coupled BEM-FEM analysis for ship hydroelasticity in waves

This paper considers the problem of ship hydroelasticity, which is an important technical issue in the design of ultra-large vessels. For the analysis of fluid-structure interaction problems, a partitioned method is applied. The fluid domain surrounding a flexible body is solved using a B-spline Rankine panel method, and the structural domain is handled with a three-dimensional finite element method. The two distinct methods are fully coupled in the time domain by using an implicit iterative scheme. The numerical results of natural frequency and the motion responses of simple and segmented barges are computed to validate the present method through comparisons with experimental and numerical results. This study extends to the application to two real ships, 6500 TEU and 10,000 TEU containerships, for more validation and also observation on the practicality of the present method. Based on this study, it is found that the present method provides reliable solutions to linear ship hydroelasticity problems.     

水下航行体波浪力理论预报

本文对水下航行体近水面航行状态进行波浪力的计算,计算采用STF理论和Frank源分布紧密拟合方法预报波浪力响应以及用Newman细长体方法和3D修正方法计算水下航行体的二阶平均波浪力与力矩.该方法和计算程序已经过多次模型试验结果比较和验证.采用该方法就某水下航行体计算了二种水深、七种相对浪向下近水面波浪力响应,并给出了波浪力参数随水深变化与浪向变化的计算结果.     

Ship hull plate processing surface fairing with constraints based on B-spline

The problem of ship hull plate processing surface fairing with constraints based on B-spline is solved in this paper. The algorithm for B-spline curve fairing with constraints is one of the most common methods in plane curve fairing. The algorithm can be applied to global and local curve fairing. It can constrain the perturbation range of the control points and the shape variation of the curve, and get a better fairing result in plane curves. In this paper, a new fairing algorithm with constraints for curves and surfaces in space is presented. Then this method is applied to the experiments of ship hull plate processing surface. Finally numerical results are obtained to show the efficiency of this method.     

EFD and CFD for KCS heaving and pitching in regular head waves

The KCS container ship was investigated in calm water and regular head seas by means of EFD and CFD. The experimental study was conducted in FORCE Technology’s towing tank in Denmark, and the CFD study was conducted using the URANS codes CFDSHIP-IOWA and Star-CCM+ plus the potential theory code AEGIR. Three speeds were covered and the wave conditions were chosen in order to study the ship’s response in waves under resonance and maximum exciting conditions. In the experiment, the heave and pitch motions and the resistance were measured together with wave elevation of the incoming wave. The model test was designed and conducted in order to enable UA assessment of the measured data. The results show that the ship responds strongly when the resonance and maximum exciting conditions are met. With respect to experimental uncertainty, the level for calm water is comparable to PMM uncertainties for maneuvering testing while the level is higher in waves. Concerning the CFD results, the computation shows a very complex and time-varying flow pattern. For the integral quantities, a comparison between EFD and CFD shows that the computed motions and resistance in calm water is in fair agreement with the measurement. In waves, the motions are still in fair agreement with measured data, but larger differences are observed for the resistance. The mean resistance is reasonable, but the first order amplitude of the resistance time history is underpredicted by CFD. Finally, it seems that the URANS codes are in closer agreement with the measurements compared to the potential theory.     

基于高阶面元法的浅水域中船-船水动力相互作用数值预报

文章开发了一种基于非均匀有理B样条（NURBS）的三维高阶面元法对浅水域中两船会遇和追越时的船-船水动力相互作用进行预报。该方法采用NURBS精确表达船体曲面,采用配置点法满足离散的边界积分方程,在边界面上的源强分布确定之后采用B样条表达物面速度势分布。基于低速假设,忽略了自由面的兴波效应,采用无穷镜像法处理刚性自由面和浅水效应,采用时间步进法在时域内求解速度势。将文中计算结果与基于RANS方程求解的CFD方法和细长体理论方法计算结果比较,验证了该方法的有效性。在此基础上,分别在不同水深、船间横向间距和船速下进行了系列的计算,分析了这些因素对船-船水动力相互作用影响。结果表明,在相同的工况下,船-船会遇时相互作用力比追越时更大,对水深变化更敏感,而对横向间距不如追越时敏感。     

基于无奇异边界元法模拟三维全非线性液舱晃荡

文章基于全非线性势流理论对三维液舱晃荡进行了数值模拟,其控制方程由无奇异边界积分方程法(Desingular-ized Boundary Integral Equation Method,DBIEM)进行离散求解,在求解全非线性的自由面微分方程时,文中采用混合欧拉—拉格朗日法(Mixed Eulerian-Lagrangian,MEL)和四阶Adams-Bashforth-Moulton(ABM4)预报—修正方法,为了避免结果发散即增强数值稳定性,文中采用B样条法来光顺自由面.在微幅水平激励下,该文中得到的结果与解析解吻合较好.     

潜艇声呐腔自噪声预报平台

本文应用统计能量分析(SEA)对潜艇声呐腔自噪声预报问题进行了研究,编制了界面友好的通用软件预报平台.计算结果与有关实验结果吻合较好,验证了预报平台的有效性和可靠性.本预报平台已应用到多型潜艇声呐腔的自噪声预报中,对选取声呐腔的声学处理方案具有重要的指导作用.     

浅水中船舶水动力特性数值计算

本文对浅水中船舶水动力特性进行数值计算研究.采用RANS方程结合RNG K-ε两方程湍流模型,对一方形系数0.6的系列60船模在浅水中的阻力、升沉、纵倾和兴波进行数值计算,其中自由面采用VOF方法处理;计算中,水深Froude数范围0.6～1.8,包含了临界和超临界水深Froude数.数值计算得到的阻力、升沉和纵倾与模型试验结果及采用三维扩展Boussinesq方程的计算结果进行了比较分析,吻合较好,部分计算结果得到改进.     

采用一种高阶面元法数值求解浅水船舶兴波问题

开发了一种基于B样条的高阶面元法用来求解浅水船舶兴波问题.船体表面和自由面上分别布置Rankine源,同时利用镜像原理来计及水底的影响.物体儿何用B样条曲面精确表示.在求得边界面卜的源强密度分布后,物面上的速度势用B样条来表示.数值计算中采用配置方法,并且用高斯-勒让德公式来计算方程中的积分.为了验证文中方法的有效性,用本方法计算了Wigley船在深水和浅水中的兴波水动力和波形,所得数值结果与试验结果和其它数值结果进行了比较,吻合程度令人满意,表明本方法被用来求解浅水船舶兴波问题是有效的.     

高速三体船波浪中运动与增阻CFD计算研究

基于数值波浪水池技术,对波浪中高速三体船运动及增阻进行CFD计算研究。控制方程—RANS方程和连续性方程使用有限体积法离散,非线性自由面采用VOF方法处理;在入口边界模拟柔性造波板运动产生入射波,使用位于波浪水池尾部的人工阻尼区消波。首先对规则波顶浪中单个主船体的运动和增阻进行了计算,并与高速细长体理论计算结果进行了比较;随后进行了三体船运动和增阻计算,分析了侧片体对主船体阻力增加的影响。为高速三体船耐波性研究提供了数值工具。     

Linear seakeeping and added resistance analysis by means of body-fixed coordinate system

This paper presents an alternative formulation of the boundary value problem for linear seakeeping and added resistance analysis based on a body-fixed coordinate system. The formulation does not involve higher-order derivatives of the steady velocity potential on the right-hand side of the body-boundary condition, i.e., the so-called m _j -terms in the traditional formulation when an inertial coordinate system is applied. Numerical studies are made for a modified Wigley I hull, a Series 60 ship with block coefficient 0.7, and the S175 container ship for moderate forward speeds where it is thought appropriate to use the double-body flow as basis flow. The presented results for the forced heave and pitch oscillations, motion responses, and added resistance in head-sea waves show good agreement with experiments and some other numerical studies. A Neumann–Kelvin formulation is shown to give less satisfactory results, in particular for coupled heave and pitch added mass and damping coefficients.     

基于多次透射公式和无奇异边界元法模拟全非线性数值波浪水池

文章基于势流理论对全非线性的三维数值水池进行了模拟,其控制方程由无奇异边界积分方程法(Desingularized Boundary Integral Equation Method,DBIEM)进行离散求解,在求解全非线性的自由面微分方程时,文中采用混合欧拉—拉格朗日法(Mixed Eulerian-Lagrangian,MEL)和四阶Adams-Bashforth-Moulton(ABM4)预报—修正方法,为了避免结果发散即增强数值稳定性,文中采用B样条法来光顺波面.同时,在远方辐射控制面上采用多次透射公式方法(Multi-transmitting Formula,MTF)来进行消波,文中得到的结果与理论解进行了比较,结果表明该方法可用来有效模拟全非线性的数值波浪水池.     

基于改进移动最小二乘法的结构可靠性分析

基于改进移动最小二乘法对结构可靠性问题进行分析,数值模拟结果表明,改进方法可有效提高计算精度.具体方法是使用椭圆范数代替二范数来度量样本点到中心点的距离,并根据上次迭代所得到的响应面在中心点处的法向量与坐标轴所成角度,对影响域进行旋转变换;从而将样本点的权重大小由样本点与中心点、响应面的距离共同决定,并将每次迭代得到的响应面函数在中心点处的法向信息包含在内.     

Two-dimensional numerical simulation and experiment on strongly nonlinear wave–body interactions

A constrained interpolation profile (CIP)-based Cartesian grid method for strongly nonlinear wave–body interaction problems is presented and validated by a newly designed experiment, which is performed in a two-dimensional wave channel. In the experiment, a floating body that has a rectangular section shape is used. A superstructure is installed on the deck and a small floating-body freeboard is adopted in order to easily obtain water-on-deck phenomena. A forced oscillation test in heave and a wave–body interaction test are carried out. The numerical simulation is performed by the CIP-based Cartesian grid method, which is described in this paper. The CIP scheme is applied in the Cartesian grid-based flow solver. New improvements of the method include an interface-capturing method that applies the tangent of hyperbola for interface capturing (THINC) scheme and a virtual particle method for the floating body. The efficiency of the THINC scheme is shown by a dam-breaking computation. Numerical simulations on the experimental problem for both the forced oscillation test and the wave–body interaction test are carried out, and the results are compared to the measurements. All of the comparisons are reasonably good. It is shown, based on the numerical examples, that the present CIP-based Cartesian grid method is an accurate and efficient method for predicting strongly nonlinear wave–body interactions.     

五体船波浪中运动与增阻的主片体协同优化研究

以波浪中的运动和增阻为目标,进行了五体船主体型线、片体主尺度和布置的协同优化。解决了型线自动变换、参数化自动建模及计算网格合并等关键技术,实现了五体船全船的自动建模。利用ISIGHT进行建模与水动力计算的集成,建立了主片体协同多目标优化系统。运用遗传算法进行多目标优化,结果表明优化后五体船运动和增阻都有所改善,并对非规则波中的情况进行了一定的探讨。