• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2001.05a
• /
• pp.70-75
• /
• 2001

Intensive experimental investigations were carried out to provide information of the effects of inflow on the rolling characteristics and stability of ships, which becomes great concern in relation to ship's capsizing. A series of systematic experiments have been performed considering the effects cf combined motion of roll-heave-sway and relevant parameters, such as roll angle and period, tank water height etc. To accommodate this type of experiments with 3-degree of freedom of motion, a bench tester has been developed and verified using existing data. Also, theoretical application of anti-roll tank has been incorporated to support the process of investigation. A model of Ro-Ro ships is used in the present study as this type of vessels, as well as fishing vessels, with large open decks, can loose stability rapidly when there is inflow on the decks.

• Journal of the Society of Naval Architects of Korea
• /
• v.37 no.1
• /
• pp.50-59
• /
• 2000

This paper presents a brief outline of dynamic stability of a damaged ship at final stage of flooding in rough beam wind and waves. One degree-of-freedom, roll equation is adopted with effects of flooding water and external forces due to wind and waves, but without effect of sloshing. We discuss the dynamic stability of the damaged ship in terms of capsizing probability based on risk analysis, the method of which was firstly proposed by Umeda et al.[6] to high speed craft in intact condition. As a result, we can evaluate the dynamic stability of the damaged ship in probabilistic manner according to sea state, operating condition and damage situation.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.13 no.1
• /
• pp.545-553
• /
• 2021

International Maritime Organization (IMO) have recently discussed the technical problems related to the second-generation intact stability criteria of ships. The second-generation intact stability criteria refer to five modes of vulnerability when the ship sailing in the ocean. In this study, we described a method to verify the criteria of the surf-riding/broaching. In case that Lv1 (Level 1) vulnerability criteria is not satisfied based on the relatively simple calculation using the Froude number (Fn), we presented the calculation procedure for the Lv2 (Level 2) criteria considering the hydrodynamics in waves. The results were reviewed based on the data for given previous ships. In absence of ship-specific data, a similar Lv2 result was confirmed by comparing the result obtained by calculating the added mass with the case where the added mass was 10% of the ship mass. This result will contribute to basic ship design process according to the IMO draft regulation.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.13 no.1
• /
• pp.746-757
• /
• 2021

To investigate the mechanism of friction-induced vibration and noise of ship water lubricated stern bearings, a two-degree-of-freedom (2-DOF) nonlinear self-excited vibration model is established. The novelty of this work lies in the detailed analysis of influence of different parameters on the stability and nonlinear vibration characteristics of the system, which provides a theoretical basis for the various friction vibration and noise phenomenon and has a very important directive meaning for low noise design of water lubricated stern bearings. The results reveal that the change of any parameter, such as rotating speed of shaft, contact pressure, friction coefficient, system damping and stiffness, has an important influence on the stability and nonlinear response of the system. The vibration amplitudes of the system increase as (a) rotating speed of shaft, contact pressure, and the ratio of static friction coefficient to dynamic friction coefficient increase and (b) the transmission damping between motor and shaft decreases. The frequency spectrum of the system is modulated by the first mode natural frequency, which is continuous multi-harmonics of the first mode natural frequency. The response of the system presents a quasi-periodic motion.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.13 no.1
• /
• pp.478-492
• /
• 2021

In this study, hull dimensions of an FPSO were optimized to maximize its operability at Brazil field. In contrast with the previous works which have used simplified models to evaluate some indicators related to stability and hydrodynamic performances of FPSOs for its own optimal design, we developed a generic hull and compartment modeler and sophisticated stability and hydrodynamic calculation modules. With the aid of the developed tools, the hull optimization was performed with initial dimensions of an FPSO originally designed for west Africa field. The optimization results indicated the relative importance of hydrodynamic performances compared with stability performances for the FPSO hull dimensioning by showing that there were 3 active constraints related to them, which were the natural periods of heave and roll and the maximum pitch angle under 1-year return period waves at full load condition. To the author's knowledge, this study is the first attempt to combine altogether the hull and compartment modeling and full set of stability and hydrodynamic calculations precisely to optimize an FPSO's hull dimensions within 30 min. Also, it is worthwhile to mention that the developed methods are generic enough to be applied to all types of ship-shaped offshore platforms.

• Journal of the Society of Naval Architects of Korea
• /
• v.43 no.1 s.145
• /
• pp.1-14
• /
• 2006

To improve maritime safety, it is very important not only to make safer design and operation but also to do proper response in case of maritime casualty. The large-scaled casualties will be caused by loss of structural strength and stability due to the progressive flooding and enlargement of damage by the effect of waves and wind. To prevent foundering and structural failure, the prediction of ship motion behavior of damaged ship in wave is necessary. This paper describes the motion behavior of damaged ship in waves through theoretical and experimental studies. A time domain theoretical model of damaged ship motions and accidental flooding, which can be applied to any type of ship or arrangement and considers the effects of flooding of compartments, has been developed. The model tests have been carried out in regular and irregular waves with different wave heights and directions in ship motion basin. Those were performed for three different damaged conditions such as engine room bottom damage, side shell damage and bow visor damage of a Ro-Ro ship. Comparison of theoretical and experimental results was performed.

• Korean Journal of Computational Design and Engineering
• /
• v.13 no.3
• /
• pp.227-234
• /
• 2008

The number of marine accidents have been decreased since various equipments for navigation control have been introduced to the marine vessels. However, disastrous marine accidents such as ship collisions are occurred more frequently. Therefore, IMO(International Maritime Organization) is enforcing the design requirement of structural strength for marine vessel. Also EU countries are developing new design methodologies and design tools to suggest the design guidance which can minimize the damage of commercial vessels in case of marine collision accidents. In this study, an integrated design system for the safety assessment has been presented to enhance the safety of damaged ships in marine collision accidents. The architecture of system is described by use-cases and IDEF functional analysis. Then an integrated system for safety assessment of damaged ship which is considering both damage stability and structural safety has been developed to support the ship design in early stage.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.26 no.4
• /
• pp.35-43
• /
• 1989

An expert system is a software program that solves problems traditionally solved only by a human expert. An expert system captures and manipulates the knowledge and strategies that a human expert applies to solve a problem. In ship design work, experience and knowledge are very important. If expert system for ship design could be developed, efficiency of design work would be increased very much through use of it. This paper is concerned with a general characteristics of expert system and development of the prototype expert system for ship design-a system which can be utilized to improve the vertical plane stability of SWATH Ship.

• Journal of Ocean Engineering and Technology
• /
• v.16 no.6
• /
• pp.71-75
• /
• 2002

In this paper, a study on the principal performance of the purse seiner ship in two vessel formations was conducted. For this task, the outline of the purse seiner fishing system in two vessel formations was reviewed. At the same time, based on the general arrangement plan, hull from of the main vessel was developed. And the stability and ship motion characteristics of the ship design were estimated. Finally, to verify the characteristics of the resistance and self-propulsion coefficient, a model test in a circulating water channel was performed. As n result, it is anticipated that this presentation will be used as the foundation material for research of purse seiner.

• Journal of Navigation and Port Research
• /
• v.33 no.9
• /
• pp.629-634
• /
• 2009

Vessels stability problems need to resolve the nonlinear mathematical models of rolling motion. For nonlinear systems subjected to random excitations, there are very few special cases can obtain the exact solutions. In this paper, the specific differential equations of rolling motion for intact ship considering the restoring and damping moment have researched firstly. Then the partial stochastic linearization method is applied to study the response statistics of nonlinear ship rolling motion in beam seas. The ship rolling nonlinear stochastic differential equation is then solved approximately by keeping the equivalent damping coefficient as a parameter and nonlinear response of the ship is determined in the frequency domain by a linear analysis method finally.