浅窄航道会遇船舶水动力相互作用数值计算

该文应用CFD软件对两船在浅窄航道中会遇时的水动力相互作用进行数值研究,通过求解非定常RANS方程并结合RNG k-ε湍流模型,采用动网格技术及UDF进行船舶运动过程中的网格更新,对两船沿平行直线航行时的三维非定常黏性流场进行数值模拟,并对其相互作用水动力进行了计算。首先通过计算结果与试验数据进行对比,验证了数值方法的可行性和有效性;随后对四种船型在不同水深、航道宽度、两船航速比和船-船横向间距下的水动力进行了系列计算,通过结果分析得出了以上因素对两船会遇水动力相互作用的影响规律。     

STUDY OF HYDRODYNAMIC FORCES OF SHIPS IN NARROW WATERWAY

1 .　INTRODUCTIONInrestricatedwaterssuchasnarrowwater ways,itisnecessarytoknowthemaneuveringcharacteristicsofships .Thecollisionofshipsisoneofthemajorreasonsofshipwreckintheworld .Thecollisionsmayoccurforavarietyofreasons .Theymaybedue ,amongotherthings ,tohumanerror ,mechanicalfailure ,weatherandwa terconditions .Butthehydrodynamicforcesbe tweentwoshipsandbetweenshipandbank ,theeffectofdepthofwateralsochangethemaneuver ingcharacteristicsofshipsgreatly .Innarrowwa terways ,specially ,the…     

基于时域格林函数的有航速船舶与波浪相互作用的数值模拟

基于深水时域格林函数的数值处理方法及开发的计算程序,采用三维时域数值模拟方法,在线性势流理论框架内对深海波浪中航行船舶的辐射问题和绕射问题进行了求解,研究探讨了航行船舶与波浪相互作用问题.研究中对不同航行速度的Wigley型船水动力系数和波浪力进行了数值计算,通过与试验及文献计算结果的比较,验证了三维时域数值计算程序的有效性.     

HYDRODYNAMIC INTERACTIONS BETWEEN TWO BODIES

On the basis of model tests, potential flow theory, and viscous Computational Fluid Dynamics (CFD) method, the hydrodynamic interactions between two underwater bodies were investigated to determine the influencing factors, changing rule, interaction mechanism, and appropriate methods describing them. Some special phenomena were discovered in two series of near-wall interaction experiments. The mathematical model and predicting methods were presented for interacting forces near wall, and the calculation results agreed well with the experimental ones. From the comparisons among numerical results with respect to nonviscosity, numerical results with respect to viscosity, and measured results, data on the influence of viscosity on hydrodynamic interactions were obtained. For hydrodynamic interaction related to multi-body unsteady motions with six degrees of freedom that is difficult to simulate in tests, numerical predictions of unsteady interacting forces were given.     

舰船在波浪中补给的运动性能研究

本文介绍舰船在波浪中补给时的运动响应理论计算方法，运用三维势流理论计算两船的水动力相互作用和波浪扰动力。根据两船的相对运动进行两船补给时的相碰概率预报。预报结果与水池船模试验进行了初步验证，吻合较好。     

浅水域中两船交错运行时的非定常波浪干涉

本文以Green-Naghdi（G-N）方程为基础,采用波动方程／有限元法计算两艘船舶在浅水域交错运动时的非定常波浪干涉特性。把运动船舶对水面的扰动作为移动压强直接包含在Green—Naghdi方程里,以描述运动船体和水面的相互作用。本文以S60 CB=0．6船为算例,给出在两艘船交错运动时,自由面波高,波浪阻力及横向力的变化特征。计算结果发现,当两艘船船首接近时,波浪阻力增加。接着,两艘船船身相向平行航行时,阻力减少。两艘船船尾相遇时,波浪阻力又增加。最后随着两船的远离,波浪阻力趋于正常。两船之间的侧向力呈现相似的变化规律。两船先承受横向排斥力,接着相互吸引,尔后又排斥。最后两船远离,横向力消失。计算结果表明,在两船间距较小和船速较大时,两船间的吸引力相当显著,应该予以充分重视。     

A TIME DOMAIN INVESTIGATION ON THE HYDRODYNAMIC RESO-NANCE PHENOMENA OF 3-D MULTIPLE FLOATING STRUCTURES

A 3-D time domain method is developed to investigate the gap influence on the wave threes for 3-D multiple floating structures. Special hydrodynamic resonance due to small gaps between multiple floating structures on wave forces is examined. Strong and complicate hydrodynamic interactions between the floating bodies are observed and the numerical computations have proved the existence of the sharp peak force response on each floating body at some special resonant wave numbers. By comparison with the results from the frequency domain technique, the results obtained from the time domain method reveal the similar resonant phenomena and hydrodynamic interaction. The resonant wave numbers are also proved around kL-nπ （n = 1,2 ……∞） with a corresponding frequency shift. The strong hydrodynamic interaction feature is practically significant for the design of module structures and the links （connection） in whole the floating body system.     

Prediction of ship-ship interactions in ports by a non-hydrostatic model

Complicated channel geometry and currents may aggravate the interactions between passing ships and berthed ships, which should be evaluated and taken into account in a port design. A method for predicting the ship-ship interactions, based on a non-hydrostatic shallow water flow model, is presented in this paper and is validated by comparing the numerical results with experimental data. The method is subsequently applied to predict the interaction forces acting on a berthed ship due to a passing ship in ports. The influences of the difference of the water depths between the dock and the main channel, the dock geometry, the current and another berthed ship in the dock on the ship-ship interactions are studied. Analysis based on the numerical results is carried out, which is useful for the port design.     

Numerical prediction of hydrodynamic forces on a ship passing through a lock with different configurations简

A CFD method is used to numerically predict the hydrodynamic forces and moments acting on a ship passing through a lock with a constant speed. By solving the RANS equations in combination with the RNG k-e turbulence model, the unsteady viscous flow around the ship is simulated and the hydrodynamic forces and moments acting on the ship are calculated. UDF is com-piled to define the ship motion. Meanwhile, grid regeneration is dealt with by using the dynamic mesh method and sliding interface technique. Under the assumption of low ship speed, the effects of free surface elevation are neglected in the numerical simulation. A bulk carrier ship model is taken as an example for the numerical study. The numerical results are presented and compared with the available experimental results. By analyzing the numerical results obtained for locks with different configurations, the influences of approach wall configuration, lock configuration symmetry and lock chamber breadth on the hydrodynamic forces and moments are demonstrated. The numerical method applied in this paper can qualitatively predict the ship-lock hydrodynamic interaction and pro-vide certain guidance on lock design.     

Valid hydrodynamic interaction regions of multiple ships advancing in waves

Based on the 3-D surface panel method combined with the translating-pulsating source Green function, an approximate approach is developed to solve the hydrodynamic interacting problem of multiple ships advancing parallel in waves. Focus is on improving the calculating efficiency. In this approach, each ship is assumed to be in each other＇s far-field, and the near-field term in this Green function is neglected if the source point falls on one ship and the field point on others. Further, a matching relationship between the far-field waves and the interfered regions, which are defined as the overlapping areas between the mean wetted body surface of one ship and the propagating regions of the waves generated by another ship, is introduced to avoid the unnecessary computation of the relative terms of the Green function, if the field point is not in the overlapping areas. The approach is validated through studying the hydrodynamic terms and the free motions of two or three ships in side-by-side arrangement by comparing the obtained results with the model tests and the predictions of the exact method. The average calculating speed for the present approximate method is about 1.65-1.8 times of that for the exact method for solving the hydrodynamic interaction problem of two ships, and 2.56-2.73 times for that of three ships.     

基于CFD的船-舵水动力干扰数值研究

该文采用基于RANS方程求解的CFD方法,对匀速直航的船-舵系统的黏性绕流场进行数值模拟,计算了不同船速和不同舵角下的船-舵水动力干扰系数,计算中忽略了自由面兴波及螺旋桨的影响。文中以KVLCC1船、舵模型为研究对象,首先将数值计算的船舶水动力及船-舵水动力干扰系数结果与模型试验数据进行比较,验证了所采用数值方法的有效性;随后,对船-舵系统、裸船体和敞水舵分别进行计算,通过水动力计算结果的比较以及流场分析,对船-舵水动力相互作用进行了数值研究。     

A 2D/3D COUPLED MODEL FOR WAVE FORCES ON MOORED SHIPS IN A HARBORA

1 .　INTRODUCTIONAccordingtoRef .[1],themotionofashipmooredagainstquayinaharborcanbestudiedintwosteps :harborwaveconditionsandwaveexcit ingforcesactingonthemooredshipshouldbegotfirst,andthendynamicresponsesofthemooringsystemincludingtheshipunderwaveexcitingforcescanbestudiedseparately .Asthefirststep ,ahybridmodelbasedonthecombinationoftheBoussinesq typeshallow waterwavemodelandthe3Dviscousflowmodelisproposedinthispaperforthetime domaincalculationofwaveexcitingforcesonmooredshipsinaharbor…     

Numerical simulation of rotating arm test for prediction of submarine rotary derivatives

The numerical method is used for predicting the rotary-based hydrodynamic coefficients of a submarine. Unsteady RANS simulations are carried out to numerically simulate the rotating arm test performed on the SUBOFF submarine model. The dynamic mesh method is adopted to simulate the rotary motions. From the hydrodynamic forces and moments acting on the submarine at different angular velocities, the rotary derivatives of the submarine can be derived. The computational results agree well with the experimental data. The interaction between the sail tip vortex and the cross flow in the hull boundary layer is discussed, and it is shown that the interaction leads to the "out-of-plane" loads acting on the submarine.     

带空泡运动航行体的附加质量研究

提出了确定带自然空泡运动物体附加质量的方法.这一方法基于在数值水洞中作摇荡运动物体的水动力计算, 包括两个主要步骤:首先采用CFD技术模拟空泡流场,求解水动力;然后根据物体运动方程,由水动力计算出附加质量.研究了带自然空泡圆盘和轴对称细长体的附加质量.计算结果与理论解一致,验证了本文方法的有效性.与切片法相比,本文方法可以更为准确地定量预报带空泡运动轴对称细长体的附加质量.     

大直径多圆柱体近海结构上的二阶辐射水动力

本文提出了一种解析方法，用来研究由海底地面动力激励引起的大直么径双圆柱体上的二阶辐射水动力问题，文中分析了激励频率和柱距等因素对二阶水动力的影响，将二阶水动力的各组成部分做了比较，还将二阶水动力与一阶水动力作了对比，并由此得出了有意义的结论。     

Hydrodynamic modelling of flow impact on structures under extreme flow conditions

Apart from the direct threat to human lives, the flood waves as a result of the rapid catchment response to intense rainfall, breaches of flood defences, tsunamis or storm surges may induce huge impact forces on structures, causing structural damage or even failures. Most existing design codes do not properly account for these impact forces due to the limited understanding of the underlying physical processes and the lack of reliable empirical formulae or numerical approaches to quantifying them. This paper presents laboratory experiments to better understand the interaction between the extreme flow hydrodynamics and the hydraulic structures and uses the measured data to validate a numerical model. The model solves the two-dimensional shallow water equations using a finite volume Godunov-type scheme for the reliable simulation of complex flow hydrodynamics. New model components are developed for estimating the hydrostatic and hydrodynamic pressure to quantify the flow impact on structures. The model is applied to reproduce two selected experiment tests with different settings and satisfactory numerical results are obtained, which confirms its predictive capability. The model will therefore provide a potential tool for wider and more flexible field-scale applications.     

NONLINEAR DIFFRACTION FORCES ON LARGE MULTICYLINDRICAL OFFSHORE STRUCTURES

ＮＯＮＬＩＮＥＡＲ　ＤＩＦＦＲＡＣＴＩＯＮ　ＦＯＲＣＥＳ　ＯＮ　ＬＡＲＧＥ　ＭＵＬＴＩＣＹＬＩＮＤＲＩＣＡＬ　ＯＦＦＳＨＯＲＥ　ＳＴＲＵＣＴＵＲＥＳＮＯＮＬＩＮＥＡＲＤＩＦＦＲＡＣＴＩＯＮＦＯＲＣＥＳＯＮＬＡＲＧＥＭＵＬＴＩＣＹＬＩＮＤＲＩＣＡＬＯＦ...     

斜向波与长棱柱型浮式结构物相互作用的边界元模拟

采用第二类变形Bessel函数对斜向线性入射波与任意截面形状的长棱柱型浮式海洋结构物的相互作用问题进行了边界元法模拟,给出了常数元和线性元的奇异积分处理方法以及开边界的处理方式。对矩形和圆形结构物的水动力系数和波浪力进行了计算,并与解析解及有限元计算结果进行了比较。结果表明,本文方法能得到满意的结果,且未出现不规则频率现象。     

THE RADIATION PROBLEM OF MULTIPLE STRUCTURES WITH SMALL GAPS IN BETWEEN

1. INTRODUCTION Recently, with the exploitation and utilization of ocean resources, various pontoon-type floating structures are widely applied. For example, Very Large Floating Structure (VLFS) is used as floating airport, multiple floating structures ar…     

TIME-DOMAIN ANALYSIS OF WAVE FORCES ON SHIPS WITH FORWARD SPEED

Analyses of wave forces on Wigley and Series 60 ships at forward speedare presented in time domain which is based on a free surface transient Green functionwith linearized condition. The main effort focus on the investigation of the numerical sta-bility of time stepping calculation and the waterline intergal contribution to the excitingforces. Numerical study shows that the stable results can be obtained when a wall-sided as-sumption is used at the stern only and the effect of waterline can be neglected. Compar-isons have been made between the present time domain calculations and other works. Nu-merical results for the added resistance on a C_B=0.8 ship in short waves are presentedbased on the assumption that the steady disturbance of ship hull can be neglected.