• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.275-280
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• 2002

Results of a numerical simulation of a flowing of the underwater vehicles hull with the pump-jet nozzle are presented. It was calculate velocity distributions and coefficients of the lift force and the longitudinal moment of the hull with the pump-jet nozzle and isolated hull for some values of angle of attack. It was shown that the area of tile influence of the nozzle on the velocities distribution of the hull and character of changing of coefficients of the lift force and the longitudinal moment and their derivatives depending on angle of attack.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.134-137
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• 2005

Recently, in VLCC, shafting system is stiffer due to large engine power whereas hull structure is more flexible due to scantling optimization, which can be suffered from alignment damage by incompatibility between shafting and hull, In this study, shafting system without stern tube forward bush was adapted for less sensitive system against external factors. Also, shaft alignment analysis was considered with hull deflection at various ship loading conditions and stern tube after bush of long journal bearing was evaluated by static squeezing pressure and dynamic oil film pressure with sloping control. Whirling vibration was also reviewed to avoid resonance with propeller blade order. So, reliable shafting design for VLCC could be achieved through optimized alignment analysis for the system without stern tube forward bush.

• Journal of computational fluids engineering
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• v.8 no.2
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• pp.42-48
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• 2003

The issues associated with the application of CFD for ship design are addressed. Doubtlessly at the moment, CFD tools are very useful in evaluating hull forms prior to traditional towing tank tests. However, time-consuming pre-processing is an obstacle in the daily application of CFD tools to improve hull forms. The accuracy of computational modeling without sacrificing the usability of CFD system is also to be assessed. The wave generation is still predicted by using potential panel methods, while velocity profiles entering into propeller plane is solved using turbulent flow solvers. The choice of turbulence model is a key to predict nominal wake distribution within acceptable accuracy. The experimental data for CFD validation are invaluable to improve physical and numerical modeling. Other applications of CFD for ship design than hull form improvement are also given. It is certain that CFD can be a cost-effective tool for the design of new and better ships.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.5-8
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• 2002

The issues associated with the application of CFD for ship design are addressed. It is quite certain that the CFD tools are very useful in evaluating hull forms a prior to traditional towing tank tests. However, the time-consuming pre-processing is an obstacle in the daily application of CFD tools to improve hull forms. The accuracy of computational modeling without sacrificing the usability of CFD system is also to be assessed. The wave generation is still predicted by using potential panel methods, while velocity profiles entering into propeller plane is solved using turbulent flow solvers. The choice of turbulence model is a key to predict nominal wake distribution within acceptable accuracy. The experimental data for CFD validation are invaluable to improve physical and numerical modeling. Other applications of CFD for ship design than hull form improvement are also given. It is certain that CFD can be a cost-effective tool for the design of new and better ships.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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• pp.147-157
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• 2011

A RANS(Reynolds averaged Navier-Stokes) based numerical method is developed for the evaluation of ship resistance and self-propulsion performances. In the usability aspect of CFD for the hull form design, the field grid around practical hull forms is generated by solving a grid Poisson equation based on the hull surface grid generated from station offsets and centerline profile. A body force technique is introduced to model the effects of the propeller in which the propeller loads are obtained from potential flow analysis using an unsteady lifting surface method. The free surface is captured by using a two-phase level-set method and the realizable $k-{\varepsilon}$ model is used for turbulence closure. The hull attitude in vertical plane, i.e., trim and sinkage, is calculated by using a quasi-steady method and then considered in the computation by translating and rotating the grid system according to the values. For the validation of the proposed method, the numerical results of resistance tests for KCS, KLNG, and KVLCC1 and of self-propulsion test for KCS are compared with experimental data.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.3
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• pp.705-715
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• 2013

This Paper presented the reduction methods of $CO_2$ emission from ships during voyage. In order to decrease $CO_2$ emission during voyage the equation was established and conducted the study about the relationship between ship speed, the propulsive efficiency and its $CO_2$ production. The results obtained from the examinations are as follows : 1. $CO_2$ emission from sailing ships can be decreased by reducing specific fuel oil consumption of main diesel engine, coefficient of total resistance and ship speed and also by increasing propeller efficiency. 2. Diesel-electric propulsion system is more effective than diesel-mechanical system to decrease the level of $CO_2$ emission during long voyage. 3. Good condition of ship's hull surface, rudder and propeller's surface can decrease the quantity of fuel oil and $CO_2$ emission by reducing the resistance of ship that can rise the propeller efficiency 4. $CO_2$ emitted from ships can be decreased in a global scale by giving attention to the synthetic transport efficiency.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.32-36
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• 2003

This paper deals with a theoretical method for the design of a biased asymmetric preswirl stator propulsion system which has been used to increase efficiency by the recovery of a propeller slipstream rotational energy by the counter rotating flow of a stator. In the case of full slow-speed ship, the upward flow is generated at the propeller plane by the after body hull form. The generated upward flow cancells the rotating flow of the propeller at the starboard part while it increases at port part. A biased asymmetric preswirl stator propulsion system consists of three blades at the port and one blade at the starboard which can recover the biased rotating flow effectively. This paper provides the design concept which gives more simple and a high degree of efficiency. The model tests for the designed compound propulsion system will be carried out later.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.3
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• pp.193-210
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• 1991

For the deckhouse or superstructure, attention is directed to the reduction of vibration from a human susceptibility point of view. The two basic requirements for obtaining a low vibration level in the accommodation are to ensure that excitation forces from propeller and/or main engine are small and to avoid resonance excitation of the hull and superstructure. In recent years increased attention has been directed towards the problems of vibration and noise in deckhouse, which have caused major problems with regard to the environmental quality in the living quarters for crews. Accordingly, in this paper, the characteristic of the vibration of deckhouse of fishing boat, of which the length/height ratio is also relatively high, are studied systematically with regard to the shape and modelling of deckhouse based on finite element method of 1-dimensional, 2-dimensional and 3-dimensional model. This study is divided into 4-part. 1st part is the global deckhouse vibration, 2nd part is the local deckhouse vibration, 3rd part consists of the estimation for stiffness of foundational support and 4th part is the application to TUNA LONG LINER of 416 ton class. For the global vibration analysis, the severity of the vibration depends on the longitudinal shear and bending stiffness of the deckhouse, on the vertical deckhouse support(fore, aft and sides). However, even if the design is technically sound, vibration problems may arise due to vertical or longitudinal hull girder or afterbody resonances. Author applied the method of this study to the analysis of, deep-sea fishing vessel of G.T. 416 ton class with relatively low height and long deckhouse, and investigated the vibrational characteristic of the fishing vessel with earlier structural feature. According to this investigation, the vibration, response of above vessel was confirmed of which main hull and deckhouse behave as one body. It is at the bottom of vibrational trouble which a accommodation part of the fishing vessel is raised, that is the local vibration for side wall, fore-aft wall and deck plate of deckhouse rather than thief fect of fore-aft vibration of deckhouse for above fishing vessel. and the resonance of main hull, deckhouse and driving system such as the main engine, propeller in exciting source is mainly brought up as the trouble.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.4
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• pp.379-388
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• 2007

Ever increasing fuel prices and environmental concerns are forcing commercial vessel operators and designers to re-assess current vessel designs with an emphasis on their propulsion systems. The most important parameter determining propulsive efficiency is the diameter of propeller. Many investigations have been carried out to adapt a large and slow turning propeller known as one of the most robust and effective way of achieving high efficiency in ship propulsion system. However, for the same vessel a further increase of propeller diameter would require the modification of the aft end while still paying attention to the hull clearance to prevent excessive propeller excited vibrations. In order to take the advantage of this approach small workboats (e.g. tug boats, fishing vessels etc.) operate in service with a significant increase of aft draught and hence resulting "inclined keel" configuration can be observed. Although it is not unusual to see large vessels sometimes to operate with stern trim to improve their operational performance and fuel efficiency, it is rare to see a such vessel purposely built with an inclined keel feature to fit a large diameter propeller for power saving. This paper investigates the application of the inclined keel configuration to a 3600TEU container vessel with the aim of fitting an 11 % larger diameter propeller (and hence resulting 17.5 % lower rpm) to gain further power saving over the similar size basis container ship with conventional "level keel" configuration.

• Journal of Ship and Ocean Technology
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• v.6 no.1
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• pp.27-33
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• 2002

Recently, the application of the electric propulsion system becomes popular because of its advantage over conventional propulsion. However, the complicated flow mechanism and interaction around the azimuth thruster are not fully understood yet, and the studies on the powering performance characteristics with azimuth/pod thrusters are now in progress. The experimental method developed in KRISO(Korea Research Institute of Ships & Ocean Engineering) is introduced and the results of the powering performance tests, consisting of resistance, self-propulsion and propeller open water tests for a cable layer with two azimuth thrusters are presented. For the analysis of powering performance with azimuth thrusters, it is necessary to evaluate the thrust/drag for components of a thruster unit, Extrapolation results could differ according to the various definitions of the propulsion unit; that is the pod, thruster leg and/or nozzle can be treated as hull appendages or as part of propulsion unit, The powering performances based on several definitions are investigated for this vessel. The results of the measurements for the 3-dimensional velocity distribution on the propeller plane are presented to understand the basis of the difference in propulsion characteristics due to the propeller rotational directions.