CFD Analysis of Ship-to-Ship Hydrodynamic Interaction

A numerical study of ship-to-ship interaction forces is performed using a commercial CFD code,and the results are compared with experimental data and with the results of a panel method analysis.Two ship models have been used in the interaction forces analysis:a tug and a tanker,advancing parallel to each other with different lateral distances and two different values of the fluid depth.Computations are carried out with four different flow models:inviscid and viscous flow with the free surface modeled as a rigid wall and inviscid and viscous flow with the deformable free surface.A fair agreement was obtained with available experimental data and results obtained by panel method.The influence of viscosity in the computations is found to be comparatively weak,while the wavemaking effects may be important,at small magnitude of the horizontal clearance.

Research on Propeller Dynamic Load Simulation System of Electric Propulsion Ship

A dynamic marine propeller simulation system was developed, which is utilized for meeting the experimental requirement of theory research and engineering design of marine electric propulsion system. By applying an actual ship parameter and its accurate propeller J＇ -KT＇ and J＇ - Kp＇ curve data, functional experiments based on the simulation system were carried out. The experiment results showed that the system can correctly emulate the propeller characteristics, produce the dynamic and steady performances of the propeller under different navigation modes, and present actual load torque for electric propulsion motor.

Dynamic Characteristic of Damaged Ship Structures Considering the Warping Deformations

For some largely damaged ships, the conventional methods are unadaptable to estimate their dynamic characteristics asto ships with symmetrical hull section. Based on dry hull modal analysis of flexure-torsion coupling vibration of unsymmetricalship structures about longitudinal center line, a transfer matrix method to calculate the dynamic characteristics is presented.Taken both shear effect and warping deformations into account, the point and field transfer matrices are derived, and the influ-

Evaluation of Hydrodynamic Coefficients of Ships Oscillating in A Numerical Wave Tank

A technique for the evaluation of the hydrodynamic coefficients of ships is outlined for ship oscillating in a numerical wave tank, which is established on Computational Fluid Dynamics （CFD） theories. The numerical simulation of ship sections and bodies forced oscillating in the tank are carried out. The added mass and damping coefficients are obtained by the decomposition of the computational results, which agree well with the corresponding ones of potential theories.

Numerical Prediction of Hydrodynamic Forces on A Ship Passing Through A Lock

While passing through a lock, a ship usually undergoes a steady forward motion at low speed. Owing to the size restriction of lock chamber, the shallow water and bank effects on the hydrodynamic forces acting on the ship may be remarkable, which may have an adverse effect on navigation safety. However, the complicated hydrodynamics is not yet fully understood. This paper focuses on the hydrodynamic forces acting on a ship passing through a lock. The unsteady viscous flow and hydrodynamic forces are calculated by applying an unsteady RANS code with a RNG k-e turbulence model. User-defined function （UDF） is compiled to define the ship motion. Meanwhile, the grid regeneration is dealt with by using the dynamic mesh method and sliding interface technique. Numerical study is carried out for a bulk carrier ship passing through the Pierre Vandamme Lock in Zeebrugge at the model scale. The proposed method is validated by comparing the numerical results with the data of captive model tests. By analyzing the numerical results obtained at different speeds, water depths and eccentricities, the influences of speed, water depth and eccentricity on the hydrodynamic forces are illustrated. The numerical method proposed in this paper can qualitatively predict the ship-lock hydrodynamic interaction. It can provide certain guidance on the manoeuvring and control of ships passing through a lock.

Dynamic response analysis of a moored crane-ship with a flexible boom

The dynamic response of moored crane-ship is studied. Governing equations for the dynamic response of a crane-ship coupled with the pendulum motion of the payload are derived based on Lagrange’s equations. The boom is modeled based on finite element method, while the payload is modeled as a planar pendulum of point mass. The dynamic response was studied using numerical method. The calculation results show that the large-amplitude responses occur at wave periods near the natural period of the payload. Load swing angle is smaller for crane-ship with flexible boom, in comparison with rigid boom. The ship surge mo- tions have large vibrations for crane-ship with flexible boom, which were not observed for a rigid boom. The analysis identifies the significance of key parameters and reveals how the system design can be adjusted to avoid critical conditions.

Dynamic analysis of multibodies system with a floating base for rolling of ro-ro ship caused by wave and slip of heavy load

Common effect of wave and slip of internal heavy load will make rolling of the roll-on ship serious. This is one of the important reasons for overturn of ro-ro ships. The multibodies System with a floating base is composed of ro-ro ship and slipping heavy load. This paper takes the rolling angle of the ship and the transverse displacement of the heavy load on desk as two freedoms. Making use of analysis of apparent gravitation and apparent buoyancy, the wave rolling moment is derived. By use of dynamic method of multibodies system with a floating base, dynamic equations of the system are established. Taking a certain channel ferry as an example, a set of numerical calculation have been carried out for rolling response of the ship and displacement response of the slipping heavy load under common effect of synchro-slipping heavy loads and wave.

Dynamic Interaction of Parallel Moving Ships in Close Proximity

现在，有许多研究，在集中于二个容器旅行并且漂浮在足够地靠近的最近经历重要相互作用的海洋的水动力学的地里进行。在波浪的平行动人的轮船的水动力学行为近来是一个有趣、重要的话题。数字调查为在常规波浪使力量和平行动人的轮船的运动回答激动的波浪的预言被执行了。数字答案基于 3D 分发技术，使用线性波浪理论决定激动强迫并且发货运动。速度效果为更现实主义的结果在格林功能被考虑了。使力量和运动回答激动的波浪的数字计算为一个水手被执行，为发现不同弗鲁德的目的的系列 60 数并且处于头海条件的不同分离距离。基于数字计算，这被揭示摇摆，滚动并且偏航由于水动力学有重要效果相互作用。

Dynamical Correction of Control Laws for Marine Ships’ Accurate Steering

这个工作的目的是为海洋的车辆自动驾驶仪设计的分析合成问题。尽管有为一个解决方案的众多的已知的方法，提及的问题由于某些动态条件，要求和限制的一张广泛的人口的存在是很复杂的，它必须被一条驾驶控制法律的适当选择满足。这份报纸的目的是简化合成的过程，提供精确的与控制系统的理想的动力学驾驶。这里建议的途径基于允许去耦的特殊统一多种用途的控制法律结构的用法合成进更简单的特别优化问题。特别地，这结构包括一个动态修正者在海波浪骚乱的行动下面为车辆鈥檚 运动支持理想的特征。作为结果，为修正者设计的一个专业化新方法被建议提供精确驾驶或在轮船的精确驾驶并且节俭的驾驶之间的一宗交易。这个方法担保关于航行的实际环境的控制法律的某个灵活性；它的相应拐弯处能在实时被认识到在上。

Numerical study on roll dynamics of damaged ship in beam waves and calm water

Computational fluid dynamics is used to study the roll dynamics of a damaged ship in beam waves with various steepnesses and in calm water.The wave-making method,which combines the velocity-inlet boundary and momentum source with the fifth-order Stokes theory,is employed for wave generation.The SST k-ωturbulence model with a modification to the turbulent viscosity in Reynolds stress is adopted to prevent the over-production of turbulence in the numerical wave tank.The lateral drift restrained model with a combined dynamic mesh strategy is utilized to deal with the coupled heave-sway-roll motions of the ship.First,benchmarking tests are performed,including wave generation and roll response of the damaged ship in regular beam waves.Then,the effects of incident wave steepness on the roll response of the damaged ship are analyzed.For different wave steepnesses,the ship roll motion is dominated by the first-order harmonic component.The second-order component increases with the increase of wave steepness.Finally,the roll hydrodynamic coefficients for different parts of the damaged ship are investigated with different rolling parameters.The added moment of inertia for the whole damaged ship is mainly attributed to the external hull composition and changes slightly with the change of roll amplitude and frequency.The added moment of inertia for the compartments could be negative in particular cases.The damping coefficients of the whole damaged ship and external hull increase with the increase of roll amplitude and frequency,while that of the compartments appears complicated with the change of roll amplitude and frequency.

A Crashworthy Device Against Ship-OWT Collision and Its Protection Effects on the Tower of Offshore Wind Farms

At present, more and more offshore wind farms have been built anti ntnnerous projects are on the drawing tables. Therefore, the study on the safety of collision between ships and offshore wind turbines （OWT） is of great practical signifieance. The present study takes the advantage of the famous LS-DYNA explicit code to simulate the dynamic proeess of the collision between a typical 3MW offshore wind turbine model with monopile fi）undation and a simplified 2000t-class ship model. In the simulation, the added mass effect of the ship, contact nonlinearity of collision, material nonlinearity of steel and aluminum foam and adaptive mesh tectmique for large structure deformation have been taken into considera- tion. Proposed is a crashworthy device for OWF of new conceptual steel sphere shell-cireular ring aluminum foam pad, and the good pe.rfurmanee of the device under the conditions of ship-OWT front impact and side impact has been verified from the views of theoretical analysis and numerical results. The new crashworthy device can effectively smooth the contact force and reduce the top structure dynamic response, using its own structure plastic deformation to absorb most of the ship collision enerty. As a result, the main structure of the OWF and the inside key electric control equipments can be saved by scarifying the structural plastic deformation of new sphere crashworthy device. What is more, the sphere configuratiun design of the crashworthy device can effectively guide the ship to run away from the main OWT structure and reduce the damage of the ship and OWT to some degree during side impact.

CFD-Based Method of Determining Form Factor k for Different Ship Types and Different Drafts

The value of form factor k at different drafts is important in predicting full-scale total resistance and speed for different types of ships. In the ITTC community, most organizations predict form factor k using a low-speed model test. However, this method is problematic for ships with bulbous bows and transom. In this article, a Computational Fluid Dynamics(CFD)-based method is introduced to obtain k for different type of ships at different drafts, and a comparison is made between the CFD method and the model test. The results show that the CFD method produces reasonable k values. A grid generating method and turbulence model are briefly discussed in the context of obtaining a consistent k using CFD.

Global Geometric Analysis of Ship Rolling and Capsizing in Random Waves

The nonlinear biased ship rolling motion and capsizing in randoro waves are studied by utilizing a global geometric method. Thompson＇ s α-parameterized family of restoring functions is adopted in the vessel equation of motion for the representation of bias. To take into account the presence of randomness in the excitation and the response, a stochastic Melnikov method is developed and a mean-square criterion is obtained to provide an upper bound on the domain of the potential chaotic rolling motion. This criterion can be used to predict the qualitative nature of the invariant manifolds which represent the boundary botween safe and unsafe initial conditions, and how these depend on system parameters of the specific ship model. Phase space transport theory and lobe dynamics are used to demonstrate how motions starting from initial conditions inside the regions bounded by the intersected manifolds will evolve and how unexpected capsizing can occur.

Sloshing-Coupled Ship Motion Algorithm for Estimation of Slosh-Induced Pressures

The effect of coupling between sloshing and ship motions in the evaluation of slosh-induced interior pressures is studied. The coupling between sloshing loads and ship motions is modelled through a hybrid algorithm which combines a potential flow solution based on transient Green function for the external ship hydrodynamics with a viscous flow solution based on a multiphase interface capturing volume of fluid(VOF) technique for the interior sloshing motion. The coupled algorithm accounts for full nonlinear slosh forces while the external forces on the hull are determined through a blended scheme of linear radiationdiffraction with nonlinear Froude-Krylov and restoring forces. Consideration of this level of nonlinearities in ship motions is found to have non-negligible effects on the slosh-coupled responses and slosh-induced loads. A scheme is devised to evaluate the statistical measure of the pressures through long-duration simulation studies in extreme irregular waves. It is found that coupling significantly influences the tank interior pressures, and the differences in the pressures between coupled and uncoupled cases can be as much as 100% or more. To determine the RAO over the frequency range needed for the simulation studies in irregular waves, two alternative schemes are proposed, both of which require far less computational time compared to the conventional method of finding RAO at each frequency, and the merits of these are discussed.

Numerical Simulation of PMM Tests for A Ship in Close Proximity to Sidewall and Maneuvering Stability Analysis

As the maneuverability of a ship navigating close to a bank is influenced by the sidewall, the assessment of ship maneuvering stability is important. The hydrodynamic derivatives measured by the planar motion mechanism （PMM） test provide a way to predict the change of ship maneuverability. This paper presents a numerical simulation of PMM model tests with variant distances to a vertical bank by using unsteady RANS equations. A hybrid dynamic mesh technique is developed to realize the mesh configuration and remeshing of dynamic PMM tests when the ship is close to the bank. The proposed method is validated by comparing numerical results with results of PMM tests in a circulating water channel. The first-order hydrodynamic derivatives of the ship are analyzed from the time history of lateral force and yaw moment according to the multiple-run simulating procedure and the variations of hydrodynamic derivatives with the ship-sidewall distance are given. The straight line stability and directional stability are also discussed and stable or unstable zone of proportional-derivative （PD） controller parameters for directional stability is shown, which can be a reference for course keeping operation when sailing near a bank.

Simulation of the Whole Process of Ship-Bridge Collision

The simulation of the whole ship-bridge collision process can be effectively carried out by nonlinear dynamic finite element method. Based on the simple description of the theory, a scenario of a 40000 DWT oil tanker colliding with a bridge across the Yangtze River is designed for simulation. The technology of structure modeling and the determination of related parameters are introduced. The deformation of the bulb bow, the history,of collision force change, the exchange of collision energy and the stress distribution. of the bridge pier-are described in detail, which: are of great value to bridge design and bridge pier damage estimation. mechanical characters in the process of ship-bridge collision are described. More accurate results can be produced by finite element method than that by empirical formulas and simplified analytical methods.

SYNCHRONOUS EFFECT OF SLIPPING HEAVY LOADS ON RO-RO SHIP ROLLING IN WAVES

Common effect of wave and slip of internal vehicles will make rolling of the roll-on ship serious. This is one of the important reasons for overturn of ro-ro ships. The multibody system with a floating base is composed of ro-ro ship and slipping vehicles. Takes the rolling angle of the ship and the transverse displacements of the slipping vehicles on desk as freedoms. Making use of the analysis of apparent gravitation and apparent buoyancy, the wave rolling moment is derived. By means of dynamic method of multibody system, dynamic equations of the system are established. Taking a certain channel ferry as an example, a set of numerical calculation have been carried out for rolling response of the multibody system with a floating base of a ro-ro ship and displacements response of the slipping vehicles under common effect of free slipping vehicles and wave, and a conclusion has been drawn that the motion of the numerous free slipping heavy loads will trend to be synchronous under restraining of the side-wall bulkhead with time because of repeated collision.

Research on the Development Strategy of Ningbo Transportation Port &Shipping Industry

Firstly, the development background of Ningbo Transportation Port & Shipping Industry is analyzed on a spatial scale. Based on that, the strategic goal of Ningbo transportation port Port & Shipping Industry is put forward, and strategic path analysis of strategic objectives is carried out. Finally, with the dynamic resource view, the strategic integration model of Ningbo Port & Shipping Industry is proposed.

SHIP HYDRODYNAMICS BASIC RESEARCH IN THE UNITED STATES

An overview of basic research on ship hydrodynamics in the United States ispresented. The focus is on leading edge research of high scientific interest bUt with ship hydrodynamics applicability. The research topic areas are briefly discussed, representative highlights from recent research are presented, and scientific hurdles to improved ship hydrodynamics technology are delineated. The purpose of the paper is to stimulate international cooperation in solving the basic research problems of common interest to all hydrodynamicists.