ABSTRACT With the development and utilization of ocean resources, maritime transportation is becoming increasingly busy. Stopping ability has great effect on the safety of ship maneuvering for those large ships. In this paper, naoe-FOAM-SJTU solver with 6DOF motion module with a hierarchy of bodies developed by Wan Decheng's research team in Shanghai Jiao Tong University is used to numerically investigate complex ship motion problem in stopping maneuver. The simulation starts from the steady state of self-propulsion and the propeller is controlled to a reverse speed to achieve the ship stopping condition. Detail information of the flow field during stopping maneuver are presented and analyzed to explain the stopping effect. The predicted results for the stopping maneuver in calm water are compared with the corresponding experimental data. The comparison is satisfactory and shows that the naoe-FOAM-SJTU solver is feasible for the direct simulation of stopping maneuvers. And the calculation results can provide suggestions when designing a ship or choosing stopping method. INTRODUCTION In recent years, ships tend to become larger for reducing the cost of shipping and improving the transport efficiency. Since the large size worsens the maneuverability, accidents can easily occur in the crowded ports and channels. Therefore, it is significant to study the stopping ability of large ships to prevent the ship from collision and to ensure the safety of the ship sailing near the port. Generally, reversing the propeller is still the most common operation when a large ship needs to brake to prevent collision. In the procedure of stopping manuever, the bow will turn left or right because of the side forces at the aft caused by reversing propeller. The existence of the transversal force caused by reversing propeller is determined by Chislett and Smitt (1972) through a ship model test. The stopping trajectory is shown in Fig. 1. Good stopping ability means minimum stopping distance, horizontal distance and yaw angle.

ABSTRACT In modern computer aided ship design system, ship hull forms are mostly represented by the Non-Uniform Rational B-Spline surfaces and saved in IGES file format for data exchange between different CAD/CAM systems. Ship hull forms represented by NURBS surfaces have many good properties including visually fair and perfectly smooth compared with hull surfaces represented by discrete meshes. The local and global deformation of NURBS surfaces is simple by relocating the NURBS control points, changing the weight of control points, which possesses strong geometric explanation and is suited for the hydrodynamic optimization of ship hull forms. Therefore, a NURBS- based hull surface modification method is developed and integrated into an in-house solver OPTShip-SJTU for the hydrodynamic optimization of ship hull forms. The developed method is applied to the hydrodynamic optimization of Series 60 model. The optimization results demonstrate that the developed method is efficient and flexible for the deformation of hull surfaces and is suited for the optimization of real life ship. INTRODUCTION With the development of computer technology and computational fluid dynamics, the CFD-based hydrodynamic optimization of ship hull forms has become a very powerful tool for the design of hull lines. It can be applied to the optimization of ship hull forms in terms of total resistance and sea-keeping performance in the preliminary stage. With the ship industry paying more and more attention to energy conservation and emission reduction such as energy efficiency design index proposed by IMO, the CFD-based hydrodynamic optimization of ship hull forms will play a more important role in the future. In general, the CFD-based hydrodynamic optimization of ship hull forms consists of four modules (Yang, 2016) including a hull surface representation and modification module, a hydrodynamic evaluation module, a surrogate module, and an optimization module. Among them, the hull surface modification module is used to modify the prototype hull forms to produce new hull forms in terms of hydrodynamic performance and design constraints. It is obvious that the ultimate optimization results are highly determined by the efficiency and quality of the hull surface modification module. The representation of hull model can be classified into two categories (Harries-Abt and Hochkirch, 2004): conventional modeling and parametric modeling. Parametric modeling defines hull model in a high level using form parameters. It can use few design variables to achieve the global deformation of ship hull forms and every form parameter has a specific meaning. But it is hard to achieve the local deformation of hull surfaces such as in the bow and stern. On the other hand, the typical example of conventional hull geometry modeling is ship hull forms represented by NURBS surfaces, which uses points to define curves and uses curves to define surfaces forming hierarchical structure. The NURBS surfaces have a simple and uniform mathematical expression to represent any complex surface as it is a mapping from two dimensional parameter space to surface in threedimensional space defined by B-spline basis function, knot vectors of parameters, NURBS control points, and weights of control points (Piegl and Tiller, 2012). It uses piecewise rational polynomials to avoid using high degree formula to fit complex surfaces and meet geometry constraints, which allows for the local deformation of hull surfaces by moving the control points and changing the weights. There are two hull surface modification method based on NURBS. One is directly moving the NURBS control points of hull surfaces. Kim (2009) selected 31 NURBS control points of Wigley hull as design variables to optimize the total drag coefficient at three given speed. Park and Choi (2013) used the movement of NURBS control points along x and z directions in the ship bow as design variables to optimize Series 60 model in terms of resistance. Wang (2015) used the direct NURBS-based hull surface modification method to generate a bulbous bow and a stern in Wigley hull. Then the hull with initial bulbous bow was optimized using radial basis function interpolation method (RBF). The direct NURBS-based hull surface modification method can achieve large and local deformation of hull surfaces. But it needs to define many design variables, which increases the computation cost. The other one is moving the NURBS control points of hull surfaces combined with other deforming methods including the RBF method, the Free Form Deformation Method and the shifting method. Noble and Clapworthy (1999) used the Free Form Deformation method (FFD) to move the control points of NURBS surfaces, which avoids the limitations of ordinary FFDs. Kim and Yang (2013) applied the shifting method and the RBF method to move the NURBS control points of Model 5279 hull to achieve the global and local deformation of ship hull forms. The optimal hull with a bulbous bow and a stern end bulb was obtained. Yang (2016) applied the NURBS-based modification technique to the optimization of a series of Joint High Speed Sealift with different bow configuration. Cheng et al (2018) employed the radial basis function interpolation method to the optimization of Series 60 model and reached a conclusion that the value of support radius of Wendland ψ 3,1 basis function has a great impact on the deformation of hull surfaces. In order to avoid generating saddle-shaped surfaces during the modification of hull surfaces, the support radius should be twice the maximum length of the Delaunay triangulation edges. Pérez et al (2007) used the cubic B-spline curves to construct the body plan of bulbous bow subject to certain form parameters and the B-spline surfaces that fit these curves were constructed. Then the initial hull with bulbous bow generated above is optimized via CFD-based optimization method. Compared with the direct NURBS-based hull surface modification method, these methods have its merits. Only a small number of control points are required as design variables to achieve the flexible deformation of hull surfaces. The large deformation of hull surfaces can be achieved where various geometry constraints can be easily satisfied. The modified region can have a fairing connection with the original hull.

Abstract The paper does test research of floating state and resistance performance for HYSWATH model with non-autonomous combination hydrofoil system, measures and analyzes the draft, trim angle of model and law of resistance with the change of navigational speed, hydrofoil position and angle of attack, test results show that the trim angle of HYSWATH model is relatively small in hull-borne, transition, foil-borne operation and different navigational status, non-autonomous combination hydrofoil system can ensure the flotation condition of HYSWATH ship model in the whole sailing process; at the same time, changes of the position and angle of attack of the front hydrofoil have a large impact on resistance properties of HYSWATH model and the speed of ship model entering into foilborne condition, and can improve the resistance performance of the ship in transient state.

Abstract The horizontal clearance effect was studied on the bending and torsion stresses in catamaran cross-deck. Also the influence of the hull geometric characteristics on the stresses of deck stringer under torsion is presented for rectangular compartment of open type ship. The computer calculations were done to study the the influence of geometrical parameters of structural elements on the stress state of ship structures. The dependences were obtained which can be used to perform an assessment of stress state of ship structures at early stages of designing and allow to preselect the structural parts with extreme stresses.

ABSTRACT: High-sped car ferries require not only high speed performance but also wide deck breadth for excellent habitability, good stability and large deadweight, giving pleasant sea travel in a short time. In this paper, aiming at further improvement in performance of high-speed ship and pursuit of the possibility of trimaran especially, wave-making mechanism and resistance characteristics were investigated by linear theory, wave analysis and resistance test. The applicability of linear theory and wave analysis to design the multi hull ship is considered. INTRODUCTION In recent years, there have been a lot of new proposals and construction of the 100m class high-speed car ferries which run by more M kts, including o n e running at the maximum speed 60 kts, and 120 m class trimaran has gone in service commission since 2005. High-speed car ferries require (1) wide deck breadth (small M) for excellent habitability, good stability and large DW and (2) high speed performance, giving pleasant sea travel in a short time. In case of mono hull, small J f l increasing wave resistance conflicts high-speed performance so the ship speed 1s limited under same engine power. In case of multi hull, small L/B can be attained easily increasing the clearance of each demihull and high-speed performance is also obtained by applying large L/B of demihull, so higher speed can be obtained comparing mono hull. In this research, aiming at further improvement in performance of high-speed multi hull ship of 45 - 60 kts (Fn=0.60 ~ 0.90) and pursuit of the possibility of trimaran especially, wavemaking mechanism and resistance characteristics were investigated by linear theory, wave analysis and resistance test. Linear wave making theory in the high-speed range, especially over last hump has been said to sufficiently well explain wave-making mechanism as compared that in medium-speed range.

ABSTRACT: A choice of engineering for mounting and disassembling work is discussed for update of the "Orlan" drilling platform for Sakhalin offshore. A common concept of mounting and dismantling work on the high hanging down constructions of the deck (that are characteristic for all drilling outfits) is considered. Main task is to provide section cuttings without cranes but with the use of special technological reinforcements. Forming principles of technological support for bulky hanging down constructions at their disassembly and installation are examined. The problems of the structural strength for this process are solved. INTRODUCTION The "Orlan" platform was exploited in the Beaufort Sea as an installation for prospecting drilling. Now it is being remodeled into a drilling platform for operation in the field of Chaivo under the "Sakhalin 1" project. Remodeling a platform out of a mobile arctic system for prospecting drilling into the "Orlan" stationary drilling platform for operation on the shelf of the island of Sakhalin has demanded special design updating, which has been made according to Rules of Russian Maritime Register (Russian Maritime Register of Shipping, 2002). One of the purposes of updating was to reduce the loads from wave slamming on overhangs of deck barges during operation of the platform on the shelf of Sakhalin. It demanded special technique. Deformations and strength of the "open" side structures were estimated to corroborate opportunity and safety of the updating work. A concept of safe process engineering of disassembling and installing barges sections using special technological supports was developed by a group of authors. The main idea was to cut the sections to be disassembled and to prepare the new ones without cranes. Description of process engineering of the work and special technological supports is the main part of this paper.

ABSTRACT: A formulation for calculating the steady hydrodynamic loading on a slender ship moving at a constant forward speed and small attack angle in finite water depth is developed. The study is motivated by the need to predict the manoeuvrability of ship with large draft in relatively shallow water. The slender body assumption is used to reduce the problem into a series of two-dimensional boundary value problems that are solved using the boundary element method. The fully non-linear free water surface conditions are imposed on the instantaneous water level. The numerical calculations are performed for the Wigley hull model ship. Effects of the attack angle and finite depth are assessed in the subcritical region. INTRODUCTION Predictions of ship manoeuvrability have drawn recent attention after the introduction of the IMO interim standards on ship manoeuvrability in 1993. The ship manoeuvrability prediction requires amongst other things, knowledge of the ship resistance and propulsion characteristics. Part of the resistance arises from the hydrodynamic forces acting on the ship body moving at a constant speed in calm seas. The hydrodynamic force computation is further complicated in that the problem is non-linear due to the non-linear boundary conditions at the unknown free water surface. The computation of ship hydrodynamics had received very significant attention in the past. Maruo and Song (1990) had developed a boundary element solution for a slender ship based on Green's functions in three-dimensions and using the Kelvin sources which satisfied the linearized free surface conditions exactly. Results were presented for the cases of a Wigley hull, a sailing yacht hull and a Series 60 C B = 0.60 hull, with good agreement with existing experimental data. They found that the non-linearity had an insignificant effect on the water surface elevation alongside the ship hull but significantly affected wave resistance.

ABSTRACT: The particle method (Moving Particle Semi-implicit method) is applied to violent free surface problems on marine engineering. The sloshing on very shallow depth condition and the very large motion of floating body with water invasion in waves are simulated successfully with it. These results show realistic behavior. INTRODUCTION After recent tragic losses of ships, many researchers have studied about the ship's damage stability and deck wetness. In these studies, they have always pointed out that behavior of water on the deck is very important. However violent free surface flow and dynamic effect of flow have hardly been considered. Almost studies of damage stability are stand on the quasi-static assumption about the behavior of water motion on the inner deck of ships. The deck wetness and the green water load acting on the structure have been treated with model experiments. In spite of an increase of computational resources in recent years, there has hardly been direct numerical simulation of these phenomena with CFD(Computational Fluid Dynamics) techniques. The reason of this exists as a difficulty in handling the violent free surface flow like fragmentation of fluid. Then VOF(Volume of Fluid Method) and its refined methods which use space fixed grid system has been used in several past studies. These methods are effective in handling violent free surface flow, but they include some of problems like numerical diffusion of free surface, stair effect, robustness of calculation and so on. Another difficulties of numerical simulation about problems exist in handling very large motion of boundary like the capsized hull. BEM(Boundary Element Method) with ALE(Arbitrary Lagrangian and Eulerian) grid has been used in researches of the numerical wave tank to simulate motion of floating body. However it is difficult to handle breaking waves, damaged hull's opening, etc. even if using ALE grid.

ABSTRACT: A comprehensive structural analysis of a 80,000 ton oil production and storage vessel is presented. The contents of the project involves the analysis of longitudinal strength, transverse strength and local strength. Among them the analysis of transverse strength and local strength are carried out by the Finite Element Method. INTRODUCTION The vessel is recently designed for offshore oil field of China. The principal dimensions of the vessel are: length L=210M, breadth B=32.8M, depth D=18.2M, draft T=11.7M. For this large vessel with complex loading conditions and particular operation requirements, it is difficult to meet the structural safety by checking the strength just simply by design Rules. Hence, it is necessary to carry out a comprehensive structural analysis by direct calculation in order to ensure the structural safety of the vessel. Based on this reason, the paper systematically deals with the structural analysis and calculation of the vessel. The ordinary-strength hull structural steel (yield stress: 235 N/mm2 ) is used in this vessel. In all cases, the check on stresses of the members is made according to the permissible stresses of DNV "Ship Rules"(l989). LONGITUDINAL STRENGTH ANALYSIS OF THE HULL The still water bending moment and shear force are calculated by an inhouse program "The Ship Structural Analysis and Design System"(SSADS). The program "SSADS" was approved by China State Shipbuilding Corporation for the standard program in China shipbuilding industry. 12 loading conditions are taken in the calculation. The largest still water bending moment and shear force of the vessel occur In loading condition l(Table 1). They are 20% and 60% larger than the corresponding values required by DNV "Ship Rules" respectively. Therefore, the modulus of the midship section should be determined by this calculated largest still water bending moment and wave bending moment worked out based on DNV "Ship Rules".

ABSTRACT: JOIA(Japan Ocean Industries Association) is continuing the research and development of a TLP(Tension Leg Platform) for the offshore petroleum production at sea of over 50Om. The major research work is focused on the development of a mooring system capable of diverless installation and a stable gravity template which allows slide to ultimate earthquake as well as waves and winds. INTROCUCTION Deep sea is one of frontier for oil production. Traditional jacket type platform is no more a special type of structure for deep water. Various types of production systems has been proposed requesting R&D of marine structures applicable with reduction of increasing cost of platform at deep-water oil fields. TLP has been applied practically at Hutton Field in North Sea in 19841 and at Green Canyon in Gulf of Mexico in 19892. TLP is considered to be a promising structure to conquer the new frontier of deep water. Japan Ocean Industries Association has organized a committee for R&D of a new concept of TLP which can be installed in the oil field of earthquake districts. The committee has worked on the discussion of a new concept of TLP which is economical and performed R&D of techniques sustaining the concept.3 However, there are no suitable estimations, because it is complex to experiment and analyze the TLP system with the seabed foundation. In this paper, we describe an experimental study of the model tests with a shaking table In a water tank on which seabed foundation is rigid, and simulate the test results with numerical analyses to investigate the stabilities of the hull and tendon mated the template due to earthquakes. And we propose to calculate the slide between the template and seabed foundation during earthquakes, and propose to calculate the settlement of template during waves.

ABSTRACT: An analytical procedure for evaluating the lateral drifting forces on SWATH ship in the beam waves is presented in the paper. By using the previously well developed strip theory and the weak scatterer assumption, the prediction of the nonlinear forces for a single ship in waves was proved to be useful. Therefore the similar way is regarded to be applicable for the estimation of the lateral drifting forces on the SWATH ship if the interaction between two hulls can be treated adequately. In the present paper a SSP model is considered and the results are shown fairly good and the weak scatterer assumption may still be regarded to be valid. INTRODUCTION The lateral drifting forces on ship in waves is an important subject for the Naval Architecture. Many analyses for the drifting forces on a single body case have been made by several authors, for example, the farfield method (Maruo, 1960), the near-field method (Kim et al, 1981) and the "weak scatterer" assumption (Salvesen, 1974), etc. The nearfield method was applied in (Fang et al, 1986) while the author (Fang, 1988) used the farfield method to estimate the lateral drifting force and moment on a SWATH ship and the better results than those of (Hong, 1983) were obtained generally. In addition to the nonlinear theory of the far-field method, the reason to reach the better results in (Fang, 1988) may be due to the application of a better strip theory (Kim et al, 1980). In the present paper, the author tries to use the existing nonlinear theory with the weak scatterer assumption (Salvesen, 1974) and the well developed strip theory (Fang, 1988) to estimate the lateral drifting forces on the SWATH ship in the beam waves.