A Time-Domain Numerical Simulation for Free Motion Responses of Two Ships Advancing in Head Waves

The constant panel method within the framework of potential flow theory in the time domain is developed for solving the hydrodynamic interactions between two parallel ships with forward speed.When solving problems within a time domain framework,the free water surface needs to simultaneously satisfy both the kinematic and dynamic boundary conditions of the free water surface.This provides conditions for adding artificial damping layers.Using the Runge−Kutta method to solve equations related to time.An upwind differential scheme is used in the present method to deal with the convection terms on the free surface to prevent waves upstream.Through the comparison with the available experimental data and other numerical methods,the present method is proved to have good mesh convergence,and satisfactory results can be obtained.The constant panel method is applied to calculate the hydrodynamic interaction responses of two parallel ships advancing in head waves.Numerical simulations are conducted on the effects of forward speed,different longitudinal and lateral distances on the motion response of two modified Wigley ships in head waves.Then further investigations are conducted on the effects of different ship types on the motion response.

Numerical Simulation on the Resistance Performance of Ice-Going Container Ship Under Brash Ice Conditions

Ice resistance prediction is a critical issue in the preliminary design of ships navigating brash ice conditions, which is closely related to the safety of a ship to navigate encounter brash ice, and has significant effects on the kinds of propellers and motor power needed. In research on this topic, model tests and full-scale tests on ships have thus far been the primary approaches. In recent years, the application of the finite element method(FEM) has also attracted interest. Some researchers have conducted numerical simulations on ship–ice interactions using the fluid–structure interaction(FSI) method. This study used this method to predict and analyze the resistance of an ice-going ship, and compared the results with those of model ship tests conducted in a towing tank with synthetic ice to discuss the feasibility of the FEM. A numerical simulation and experimental methods were used to predict the brash ice resistance of an ice-going container ship model in a condition with three concentrations of brash ice(60%, 80%, and 90%). A comparison of the results yielded satisfactory agreement between the numerical simulation and the experiments in terms of both observed phenomena and resistance values, indicating that the proposed numerical simulation has significant potential for use in related studies in the future.

Numerical Simulation on Ship Bubbly Wake

Based on a volume of fluid two-phase model imbedded in the general computational fluid dynamics code FLUENT6.3.26, the viscous flow with free surface around a model-scaled KRISO container ship （KCS） was first numerically simulated. Then with a rigid-lid-free-surface method, the underwater flow field was computed based on the mixture muitiphase model to simulate the bubbly wake around the KCS hull. The realizable k-e two-equation turbulence model and Reynolds stress model were used to analyze the effects of turbulence model on the ship bubbly wake. The air entrainment model, which is relative to the normal velocity gradient of the free surface, and the solving method were verified by the qualitatively reasonable computed results.

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.

High Resolution Ship Hydrodynamics Simulations in Open Source Environment

The numerical simulation of wake and flee-surface flow around ships is a complex topic that involves multiple tasks： the generation of an optimal computational grid and the development of numerical algorithms capable to predict the flow field around a hull. In this paper, a numerical framework is developed aimed at high-resolution CFD simulations of turbulent, free-surface flows around ship hulls. The framework consists in the concatenation of ＂tools＂, partly available in the open-source finite volume library OpenFOAM. A novel, flexible mesh-generation algorithm is presented, capable of producing high-quality computational grids for free-surface ship hydrodynamics. The numerical frame work is used to solve some benchmark problems, providing results that are in excellent agreement with the experimental measures.

Numerical Simulation and Analysis of Electromagnetic Fields Induced by a Moving Ship Based on a Three-Layer Geoelectric Model

In this paper,we present a numerical simulation method of electromagnetic(EM)fields induced by a moving ship(EMFMS),which consist of both the shaft-rate EM field and the static EM field.The shaft-rate EM fields in the frequency domain are first obtained by solving the partial differential equations together with suitable boundary conditions,and then they are transformed into the time domain by using the inverse Fourier transform.Finally,the static fields are added to obtain the EM fields of a moving ship.The effects of the source current intensity and the source position on the EM fields of a moving ship are discussed in detail.A field example of EM response of a moving ship is presented and its characteristics are analyzed.

Numerical Simulations of Pile Supported Protective System Subjected to Ship Impact

The head-on collision process between ship and concrete pile supported protective system is simulated by software LS-DYNA. The influences of pile non-linearity and soil non-linearity on impact force, ship crush depth and the cap displacement of pile supported protective system are discussed. It's shown that for both severe impact case and non-severe impact case, the non-linearity of pile material influence the impact force history, ship crush depth. The non-linearity of pile material and soil has remarkable influence on the cap displacement especially for severe impact case. These issues should not be ignored in the analysis of pile supported protective system subjected to ship impact.

Simulation System Design of 3-D Panorama of Ship Motions in Wave

In this paper a 3-D panoramic simulation system of a ship is described which is developed with the MAXSCRIPT language and VC++ as programming tools on the platform of 3Dsmax. The strip theory method is applied to the motion prediction of the mono-hull. The time history solutions of heave and pitch are obtained in the condition of head sea to provide the primary data on panoramic simulation. The simulation system has following functions: 1)digital simulation;2) panoramic simulation; 3) environmental set-up; 4) render preview and output.

Study on the Simulation and Run-up of Ship Waves of Express Liners in the Zhujiang Delta

Ship waves are observed with wave-generating techniques by way of simulating express liners in the Zhujiang Delta.The analog test study of ship waves is conducted in a wave flume and a wave basin respectively. Thus, different wave elements and different incident angles of ship waves are decided; so are different slopes of protection, the plafform, width of plafform, and the influence over the ship wave run-up on protection from armor coat structure. The empirical relation-

Practical Solutions for Reducing Container Ships' Waiting Times at Ports Using Simulation Model

The main challenge for container ports is the planning required for berthing container ships while docked in port.Growth of containerization is creating problems for ports and container terminals as they reach their capacity limits of various resources which increasingly leads to traffic and port congestion.Good planning and management of container terminal operations reduces waiting time for liner ships.Reducing the waiting time improves the terminal’s productivity and decreases the port difficulties.Two important keys to reducing waiting time with berth allocation are determining suitable access channel depths and increasing the number of berths which in this paper are studied and analyzed as practical solutions.Simulation based analysis is the only way to understand how various resources interact with each other and how they are affected in the berthing time of ships.We used the Enterprise Dynamics software to produce simulation models due to the complexity and nature of the problems.We further present case study for berth allocation simulation of the biggest container terminal in Iran and the optimum access channel depth and the number of berths are obtained from simulation results.The results show a significant reduction in the waiting time for container ships and can be useful for major functions in operations and development of container ship terminals.

Simulation and Reasonable Design of Bridge Steel Fenders to Reduce Ship Impacts

Steel fenders are increasingly used for ship-impact resistance structures in the design of navigable bridges. As an important approach to investigating this anti-impact structure effectiveness to reduce influences of vessel impact, simulation analyses are still not perfect yet. So this paper is intended to discuss several issues related to ship collision simulations, including steel constitutive relationship, connections between steel box and pile cap, contacts definition and friction consideration, and the determination of impact waterlines and angles. Consequently based on two examples of ship-steel fender-bridge structure systems, some conclusions about effectiveness and design of fenders to reduce ship impact are drawn.

Optimization Parameter of Transformation of Parallel Translation for Ship Pitch Simulation

The transformation of parallel translation can improve the smoothness of discrete series sometimes. In this paper, for ship pitch, a method to modify the system error is proposed via the transformation of parallel translation, which can give the optimize parameters using the Method of Minimum Squares. The series in the method can fit white exponential law better, and then be applied in GM (1,1) very well. The numerical experiments imply that the method is practical, which make the ship pitch system model more accurate than GM ( 1,1 ).

基于Simulation X的舰船传动系统性能仿真与分析

传动系统是舰船的重要组成部分,包括曲轴、减速器等,传动系统的抗冲击性、柔性等特性是船舶正常运行的基础。本文为了系统地探究船舶传动系统的振动及抗冲击性能,利用三维建模软件UG建立传动系统的模型,并利用Simulation X仿真平台进行了船舶传动系统和液压控制回路的仿真试验。

基于Plant Simulation的船厂平直车间作业仿真与优化

船体分段的制造在整个船舶生产过程中占据了大量时间,因此,缩短分段制造时间是缩短船舶建造周期、降低建造成本、提高船厂生产效率的关键所在。以船厂平直车间为研究对象、以缩短车间生产平面分段的最大流程时间为目标,使用Plant Simulation对平面分段的生产制造流程进行模拟仿真,并基于仿真结果使用内置遗传算法功能模块对分段生产顺序进行优化处理,以达到缩短最大流程时间的目的,对分段车间的生产排程具有实际意义。

Formal safety assessment and application of the navigation simulators for preventing human error in ship operations

The International Maritime Organization (IMO) has encouraged its member countries to introduce Formal Safety Assessment (FSA) for ship operations since the end of the last century. FSA can be used through certain formal assessing steps to generate effective recommendations and cautions to control marine risks and improve the safety of ships. On the basis of the brief introduction of FSA, this paper describes the ideas of applying FSA to the prevention of human error in ship operations. It especially discusses the investigation and analysis of the information and data using navigation simulators and puts forward some suggestions for the introduction and development of the FSA research work for safer ship operations.

Modeling and designing for ship steering integrated simulator

The modeling of a ship steering integrated simulator(SSIS)applied to the design,debugging and maintenance of an autopilot is discussed.A nonlinear responsive model is proposed and applied to the design of SSIS.The SSIS generates real signals of the ship heading,the rudder angle,the ship position and the output to the autopilot.A variety of factors,such as ship speed variety,shallow water effect,nonlinearity of yaw and actuator,and environmental disturbances like wind,wave and current are considered carefully.Detailed formulas for calculating relevant parameters are provided.Taken a naval ship as an example,the physical-digital simulations on SSIS and the digital simulation on a Marine System Simulator(MSS)were conducted separately in various sailing conditions.Simulation results show that the simple nonlinear responsive model can be applied to ship motion control and simulation with sufficient accuracy and effectiveness.

Evaluation and selection of the ship collaborative design resources based on AHP and genetic and simulated annealing algorithm

The characteristics of the design resources in the ship collaborative design is described and the hierarchical model for the evaluation of the design resources is established. The comprehensive evaluation of the co-designers for the collaborative design resources has been done from different aspects using Analytic Hierarchy Process （AHP） ,and according to the evaluation results,the candidates are determined. Meanwhile,based on the principle of minimum cost,and starting from the relations between the design tasks and the corresponding co-designers,the optimizing selection model of the collaborators is established and one novel genetic combined with simulated annealing algorithm is proposed to realize the optimization. It overcomes the defects of the genetic algorithm which may lead to the premature convergenee and local optimization if used individually. Through the application of this method in the ship collaborative design system,it proves the feasibility and provides a quantitative method for the optimizing selection of the design resources.

Influence of sway motion on passive anti-rolling tank

The passive anti-rolling tank is one of important ship stabilizers widely used today. But at present, research of the tank is most aimed at its rolling movement. In this paper, the influence of sway motion on the passive anti-rolling tank is considered, the mathematical model of ＂ship-passive antl-rolling tank＂ system coupled with sway motion is developed basing on the U-shaped passive anti-rolling tank theory. Both simulation results and experimental data indicate that it is necessary to consider the influence of sway motion on the anti-rolling tank, which is more agreeable to the actual circumstance.

A Virtual Erection Simulation System for a Steel Structure Based on 3-D Measurement Data

he virtual erection simulation system was explained for a steel structure including ship and ocean plant blocks. The simulation system predicted the erection state to optimize any gap or overlap of blocks based on 3-D measurement data. The blocks were modified （cut） on the basis of the simulation result on the ground before erecting them by crane. The re-cutting process was not required and the blocks were erected into a mother ship speedily. Therefore, the erection time is reduced, increasing the dock turnover.

A Full Mission Simulator of the Ship＇s Automated Electric Power System for Training and Competence Testing of Marine Engineers

This article describes practical preparation of marine engineers on the full mission simulator complex of the ship＇s automated electrical power plant. A full mission simulator complex of the ship＇s automated power management system meets International Convention STCW （Standards of Training, Certification and Watchkeeping） 78 （with Manila amendments 2010） requirements in part of adequate reproduction of its operational modes corresponding to the actual configuration and layout of the ship＇s automated power management system with real consumers and typical loads. The simulator is fully consistent with the goals and objectives of the practical training, as well as the goals and objectives of proficiency testing engine department officers on issues of technical maintenance of real ship＇s equipment （high voltage installations included） and means of automation. The simulator＇s complex is designed for training and proficiency testing of cadets and students of maritime educational institutions, as well as training and proficiency testing of marine specialists （mechanics and electricians） by watch-keeping and maintenance of modem integrated automated control systems of ship＇s electric power plant and the individual ship electromechanical systems, including high-voltage systems. A simulator＇s complex provides adequate reproduction of operational situations on technical side of real ship electric and automation equipment provides training on monitoring, control and management diesel-generator sets in hand, semi-automatic and automatic modes of power station, control and management of electromechanical systems, as well as the set of tasks upon parameterization, visualization and etc. Besides number of combinations of monitoring, control and management tasks, the simulator＇s complex provides an opportunity to simulate various practical fault conditions. It allows students to focus on the work of automatic control system in emergency situations and to work out correct actions for a watch-keeper on searching, localizing of faults and troubleshooting of equipment.