The choice of speed and clearance for RAS on 3D method

In this paper, a 3D source distribution technique is used to calculate the coupled motions between two ships which advance in the wave with the same speed. The numerical results of coupled motions for a frigate and a supply ship have a good agreement with the experimental results. Based on the 3D coupled motions of two ships, a spectral analysis is employed to clearly observe the effect of speed, clearance and wave heading on the significant relative motion amplitude (SRMA) of two ships.The method presented in this paper will be helpful to select suitable clearance, speed and wave heading for underway replenishment at sea(RAS).     

海上结构管状TY接头平面内弯曲和平面外弯曲引起的载荷应力集中因素分析（英文）

The aim of this work is to study the stress distributions and the location of hot spots stress in the vicinity of the intersection lines of the tubular elements of the tubular TY-joints. Using the finite element models, we analyze the effects of geometrical parameters on the stress concentration factor in the case of in-plane bending and out-of-plane bending loads, around the weld toe of the tubular joints. Our results reveal the location of the maximum stress concentration factor at the heel or...     

Coupled motions of two ships in irregular waves in time domain

A three-dimensional time domain approach is used to study the coupled motions of two ships with forward speed in waves. In this approach, the boundary condition is satisfied on the mean wetted hull surface of the moving bodies and the free surface condition is linearized. The problem is solved by using a transient free-surface Green function source distribution on the submerged hulls. After solving the response amplitude operator, the method of spectral analysis is employed to clearly express the motion energy spectrum and significant amplitude of two ships. For verifying the code, two same circular cylinders at beam wave are selected to calculate coupled motions by comparison with the results obtained by 3D frequency method which has been proved to be efficient for solving such problems.Two Wigley ships of different sizes with the same forward speed are chosen for numerical calculation of the interaction effect, and some useful suggestions are obtained for underway replenishment at sea.     

17000载重吨油船结构疲劳分析的快速估算方法(英文)

Fatigue cracks and fatigue damage have been important issues for ships and offshore structures for a long time.However,in the last decade,with the introduction of higher tensile steel in hull structures and increasingly large ship dimensions,the greater attention should be paid to fatigue problems.Most research focuses on how to more easily access the fatigue strength of ships.Also,the major classification societies have already released their fatigue assessment notes.However,due to the complexity of factors influencing fatigue performances,such as wave load and pressure from cargo,the combination of different stress components,stress on concentration of local structure details,means stress,and the corrosive environments,there are different specifications with varying classification societies,leading to the different results from different fatigue assessment methods.This paper established the Det Norske Veritas(DNV) classification notes "fatigue assessment of ship structures" that explains the process of fatigue assessment and simplified methods.Finally,a fatigue analysis was performed by use data of a real ship and the reliability of the result was assessed.     

国际海事组织船舶能效提案及其影响综述（英文）

This paper presents a review of the different International Maritime Organization(IMO) initiatives to improve the ship energy efficiency of new and existing ships, which is considered one of the essential tasks to reduce Greenhouse Gas(GHG) in the maritime industry. First, the IMO effort and initiatives and the different indices suggested by the IMO are presented till the last version of the Marine Environment Protection Committee(MEPC), showing the effect of different technologies on reducing t...     

搅拌工具轴肩和搅拌头轮廓对铝合金搅拌摩擦焊的影响一对比研究(英文)

In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to steel.In this paper a study on friction stir welding of aluminum alloys was presented.The present investigation deals with the effects of different friction stir welding tool geometries on mechanical strength and the microstructure properties of aluminum alloy welds.Three distinct tool geometries with different types of shoulder and tool probe profiles were used in the investigation according to the design matrix.The effects of each tool shoulder and probe geometry on the weld was evaluated.It was also observed that the friction stir weld tool geometry has a significant effect on the weldment reinforcement,microhardness,and weld strength.     

Experimental observation and computer simulation on non-equilibrium grain-boundary segregation kinetics of phosphorus

An experimental study and computer simulation on non-equilibrium grain-boundary segregation kinetics and the critical time for phosphorus in 12Cr1MoV steel( which is used in steam pipeline of ships)are put forward in this paper. The segregation level of phosphorus with solution temperature 1050 ℃ at the isothermal holding temperature of 540 ℃ ,have been measured at grain-boundaries. A non-equilibrium grain-boundary segregation kinetics curve of phosphorus is given, The critical time for phosphorus non-equilibrium grain-boundary segregation is about 500 h at 540 ℃ for the experimental steel, When the holding time is longer than 1 500 h, non-equilibrium segregation disappears and the level of segregation reaches full equilibrium, The simulation using the kinetic equations of non-equilibrium grain-boundary segregation is in good accordance with the experimental observation for phosphorus in steel 12Cr1 MoV. The non-equilibrium grain-boundary segregation kinetic model is therefore proved.     

导流板对弯管流激噪声和流致振动的影响(英文)

The effect of a guide vane installed at the elbow on flow-induced noise and vibration is investigated in the range of Reynolds numbers from 1.70×105 to 6.81×105, and the position of guide vane is determined by publications. The turbulent flow in the piping elbow is simulated with large eddy simulation(LES). Following this, a hybrid method of combining LES and Lighthill's acoustic analogy theory is used to simulate the hydrodynamic noise and sound sources are solved as volume sources in code Actran. In addition, the flow-induced vibration of the piping elbow is investigated based on a fluid-structure interaction(FSI) code. The LES results indicate that the range of vortex zone in the elbow without the guide vane is larger than the case with the guide vane, and the guide vane is effective in reducing flow-induced noise and vibration in the 90° piping elbow at different Reynolds numbers.     

Optimization of bow shape for a non ballast water ship

In this research,a commercial CFD code ＂Fluent＂ was applied to optimization of bulbous bow shape for a non ballast water ships（NBS）.The ship was developed at the Laboratory of the authors in Osaka Prefecture University,Japan.At first,accuracy of the CFD code was validated by comparing the CFD results with experimental results at towing tank of Osaka Prefecture University.In the optimizing process,the resistances acting on ships in calm water and in regular head waves were defined as the object function.Following features of bulbous bow shapes were considered as design parameters： volume of bulbous bow,height of its volume center,angle of bow bottom,and length of bulbous bow.When referring to the computed results given by the CFD like resistance,pressure and wave pattern made by ships in calm water and in waves,an optimal bow shape for ships was discovered by comparing the results in the series of bow shapes.In the computation on waves,the ship is in fully captured condition because shorter waves,λ/Lpp 0.6,are assumed.     

Influence of external restraint distribution on welding buckling of thin plate butt joint北大核心CSCD

［Objectives］It is easy to produce buckling distortion when welding thin plate butt joints, which affects the construction period, cost and performance, but this can be controlled by applying external restraints. ［Methods ］ First, a butt welding test of a thin plate under external restraints is carried out, and the out-of-plane deformation is measured by the optical surface scanning method. At the same time, finite element (FE) models in a free state and external restraint state are established, and the thermal mechanical phenomena of the two models are subjected to thermal-elastic-plastic FE analysis (TEP FE). The influence of different external restraint distributions on the welding buckling distortion of the joints is then studied, and reasons for controlling welding buckling distortion are analyzed from the perspective of longitudinal plastic strain and longitudinal contraction force.［Results ］ The out-of-plane deformation of the corresponding model is in good agreement with the measured results, and milder than the out-of-plane deformation of the model in a free state. When external restraints are applied, the longitudinal plastic strain of the weld and its adjacent metal decreases, and the longitudinal contraction force of the thin plate also decreases.［Conclusions ］ The results verify that external restraints can effectively control welding buckling distortion, and the control effects are different depending on the external restraint distribution. © 2023 Chinese Journal of Ship Research. All rights reserved.     

柔性浮式结构上浪载荷数值模拟的CFD-BEM-FEM三步法（英文）

In this paper, the effect of green water impact on a flexible structure is studied based on three-step computational fluid dynamics(CFD)–boundary element method(BEM)–finite element method(FEM) approach. The impact due to shipping of water on the deck of the vessel is computed using commercial CFD software and used as an external force in coupled BEM-FEM solver. Other hydrodynamic forces such as radiation, diffraction, and Froude-Krylov forces acting on the structure are evaluated using 3 D time domain panel method. To capture the structural responses such as bending moment and shear force, 1 D finite element method is developed. Moreover, a direct integration scheme based on the Newmark–Beta method is employed to get the structural velocity,displacement, etc., at each time step. To check the effect of the green water impact on the structure, a rectangular barge without forward speed is taken for the analysis. The influence is studied in terms of bending moment, shear force, etc. Results show that the effect of green water impact on the bow region can be severe in extreme seas and lead to various structural damages. Similarly,it is also verified that vessel motion affects green water loading significantly and therefore one must consider its effect while designing a vessel.     

Multi-objective optimization study on dimensions of medium-sized cruise ship in concept phase北大核心CSCD

［Objective］Aiming at the problem of too many influencing factors and too little reference data for determining the dimensions of medium-sized cruise ships in the concept phase, a simplified multi-objective optimization method based on the fitting of dimensions and performance is proposed. ［Method］First, the dimension relations of medium-sized cruise ships are analyzed and the influence of the latest SOLAS requirements used to determine the optimization range. Second, the influence of cruise ship dimensions on space, resistance, stability and seakeeping are analyzed. Next, based on the principles of genetic algorithms, a multiobjective optimization algorithm with high robustness and high engineering adaptability is determined to establish a multi-objective optimization model for the concept design of medium-sized cruise ships. Finally, the Pareto solution obtained by multi-objective optimization is analyzed to provide initial references for determining the dimensions of the target cruise ship. ［Results］Implemented via a genetic algorithm, the optimization program proposed herein is applied in the concept design of a medium-sized cruise ship in order to optimize the initial dimensions, thereby achieving the expected outcome of providing reasonable initial dimensions for cruise ship design. ［Conclusion ］ The proposed simplified multi-objective optimization model can provide feasible initial dimensions for medium-sized cruise ships in the concept phase. As the Pareto solution obtained by multi-objective optimization has different focuses such as resistance and stability, the most suitable solution needs to be selected according to the design object. © 2023 Chinese Journal of Ship Research. All rights reserved.     

航行于波浪中的肥大型船波浪增阻计算研究(英文)

Under the background of the energy saving and emission reduction, more and more attention has been placed on investigating the energy efficiency of ships. The added resistance has been noted for being crucial in predicting the decrease of speed on a ship operating at sea. Furthermore, it is also significant to investigate the added resistance for a ship functioning in short waves of large modern ships. The researcher presents an estimation formula for the calculation of an added resistance study in short waves derived from the reflection law. An improved method has been proposed to calculate the added resistance due to ship motions, which applies the radiated energy theory along with the strip method. This procedure is based on an extended integral equation (EIE) method, which was used for solving the hydrodynamic coefficients without effects of the irregular frequency. Next, a combined method was recommended for the estimation of added resistance for a ship in the whole wave length range. The comparison data with other experiments indicate the method presented in the paper provides satisfactory results for large blunt ship.     

Numerical study of viscous wave-making resistance of ship navigation in still water

The prediction of a ship＇s resistance especially the viscous wave-making resistance is an important issue in CFD applications. In this paper, the resistances of six ships from hull 1 to hull 6 with different hull forms advancing in still water are numerically studied using the solver naoe-FOAM-SJTU, which was developed based on the open source code package OpenFOAM. Different components of the resistances are computed and compared while considering two speed conditions （12 kn and 16 kn）. The resistance of hull 3 is the smallest while that of hull 5 is the largest at the same speed. The results show hull 3 is a good reference for the design of similar ships, which can provide some valuable guidelines for hull form optimization.     

Fatigue analysis of the bow structure of FPSO

The bow structure of FPSO moored by the single mooting system is rather complicated. There are many potential hot spots in connection parts of structures between the mooting support frame and the forecastle. Mooting forces, which are induced by wave excitation and transferred by the YOKE and the mooting support frame, may cause fatigue damage to the bow structure. Different from direct wave-induced-forces, the mooting force consists of wave frequency force (WF) and 2nd draft low frequency force (LF) , which are represented by two sets of short-term distribution respectively. Based on two sets of short-term distribution of mooting forces obtained by the model test, the fatigue damage of the bow structure of FPSO is analyzed, with emphasis on two points. One is the procedure and position selection for fatigue check, and the other is the application of new formulae for the calculation of accumulative fatigue damage caused by two sets of short-term distribution of hot spot stress range. From the results distinguished features of fatigue damage to the FPSOs bow structure can be observed.     

水下爆炸空化效应作用下全船响应的并行计算(英文)

As well as shock wave and bubble pulse loading, cavitation also has very significant influences on the dynamic response of surface ships and other near-surface marine structures to underwater explosive loadings. In this paper, the acoustic-structure coupling method embedded in ABAQUS is adopted to do numerical analysis of underwater explosion considering cavitation. Both the shape of bulk cavitation region and local cavitation region are obtained, and they are in good agreement with analytical results. The duration of reloading is several times longer than that of a shock wave. In the end, both the single computation and parallel computation of the cavitation effect on the dynamic responses of a full-scale ship are presented, which proved that reloading caused by cavitation is non-ignorable. All these results are helpful in understanding underwater explosion cavitation effects.     

Statistical Analysis of Ship Collisions with Bridges in China Waterway

Having carried out investigations on ship collision accidents with bridges in waterway in China, a database of ship collision with bridge (SCB) is developed in this paper. It includes detailed information about more than 200 accidents near ship' s waterways in the last four decades, in which ships collided with the bridges. Based on the information a statistical analysis is presented tentatively. The increase in frequency of ship collision with bridges appears, and the accident quantity of the barge system is more than that of single ship. The main reason of all the factors for ship collision with bridge is the human errors, which takes up 70%. The quantity of the accidents happened during flooding period shows over 3 - 6 times compared with the period from March to June in a year. The probability follows the normal distribution according to statistical analysis. Visibility, span between piers also have an effect on the frequency of the accidents.     

12毫米厚铝合金板的搅拌摩擦焊研究(英文)

Most of the investigations regarding friction stir welding(FSW)of aluminum alloy plates have been limited to about 5 to 6mm thick plates.In prior work conducted the various aspects concerning the process parameters and the FSW tool geometry were studied utilizing friction stir welding of 12 mm thick commercial grade aluminum alloy.Two different simple-tomanufacture tool geometries were used.The effect of varying welding parameters and dwell time of FSW tool on mechanical properties and weld quality was examined.It was observed that in order to achieve a defect free welding on such thick aluminum alloy plates,tool having trapezoidal pin geometry was suitable.Adequate tensile strength and ductility can be achieved utilizing a combination of high tool rotational speed of about 2000 r/min and low speed of welding around 28 mm/min.At very low and high dwell time the ductility of welded joints are reduced significantly.     

基于模糊集合的船舶燃气轮机临界因素的Dematel评估方法（英文）

In power production, gas turbines are commonly used components that generate high amount of energy depending on size and weight. They function as integral parts of helicopters, aircrafts, trains, ships, electrical generators, and tanks. Notably, many researchers are focusing on the design, operation, and maintenance of gas turbines. The focal point of this paper is a DEMATEL approach based on fuzzy sets, with the attempt to use these fuzzy sets explicitly. Using this approach, the cause–effect diagram of gas turbine failures expressed in the literature is generated and aimed to create a perspective for operators. The results of the study show that, "connecting shaft has been broken between turbine and gear box" selected the most important cause factor and"sufficient pressure fuel does not come for fuel pump" is selected the most important effect factor, according to the experts.     

Assessment of Electric Power Quality in Ships＇ Modern Systems

The paper deals with the selected problems of electric power quality in ships‘ modern systems.In the introduction the fundamentals of electric power quality assessment, such as the relations and consequences among power quality phenomena and indices, secondly as the methods and tools as well as the appropriate instrumentation, have been shortly presented. Afterwards, the basic characteristic of power systems on modern ships has been given. The main focus of the paper is put on the assessment of electric power quality in ships‘ systems fitted with converter subsystems. The state of the art and actual tendencies in the discussed matter have been shown. Some chosen experimental results, based on the research carried out under supervision of the author, have been presented, too. Finally, some concluding issues have been shortly commented on.