• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.66-71
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• 2006

To develope a hull form of catamaran type dredging vessel, resistance characteristics is investigated to find the interaction effect of waves between the two hulls. Re fore body shape is simplified as two dimensional wedge shape for the maintenance and disassembly/assembly. Based on MAC method, numerical simulation is performed in staggered variable mesh system. Re conservation form of Euler equations and continuity equation are applied as governing equations. To verify numerical methods, the wive patterns along the hull surface are compared with the results of model tests. This study is performed as varying wedge shape of the bow and the distance between the two hulls. The wave interaction between two hulls are observed to investigate the relation the resistance performance and the flow characteristics. Suitable hull form and distance between two hulls are discussed.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.6
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• pp.312-321
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• 2020

In this study, machine learning techniques were applied to predict the residual resistance coefficient (Cr) of low-speed full ships. The used machine learning methods are Ridge regression, support vector regression, random forest, neural network and their ensemble model. 19 hull form variables were used as input variables for machine learning methods. The hull form variables and Cr data obtained from 139 hull forms of KRISO database were used in analysis. 80 % of the total data were used as training models and the rest as validation. Some non-linear models showed the overfitted results and the ensemble model showed better results than others.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.400-409
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• 2016

In recent, shipping companies have made an enormous effort to improve the operation of vessel in various approaches, due to recession of shipping market and increasing competition among shipping companies. One of important parameters for improving the efficiency of vessel is the resistance performance that consist of friction and residual resistance. Especially, it is recognized that the friction resistance tends to be affected by conditions of vessel’s surface and occupies approximately 70~90% of the total resistance for slow speed ships. In general, the surface of vessel is covered with various type of paint to reduce fouling and corrosion. As time goes by, however, it is so hull roughness would be increased by fouling over the wetted surface that anti-fouling paints, such as CDP(Controlled Depletion Paint), Tin-Free SPC(Self Polishing Co-polymer) or Foul Release, are applied evenly on the hull surface. Nevertheless, these anti-fouling paints could not prevent fouling absolutely. A fundamental study on evaluating ship resistance performance variation due to hull roughness has been performed using a commercial software, Star-CCM+, which solves the continuity and Navier-Stokes equations for incompressible and viscous flow. The results of present simulation for plate are compared with some experimental data available and the effect of surface roughness to ship resistance performance is discussed.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.4 s.142
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• pp.341-349
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• 2005

With increasing demands of high speed transportation, recently a lot of high speed marine vehicles, such as SWATH, semi-planing craft, planing craft, hydrofoil craft, SES and so on, have been paid attention especially in high speed region over the Froude number 0.5. The resistance characteristics of the vehicles should be experimentally evaluated in the towing tank. At the Seoul National University, a light-weight cantilever type towing carriage was devised and installed in the towing tank. Wireless measurement devices were also provided for appropriate data acquisition during high-speed towing tests. With the new carriage system, a series of model tests were performed to investigate the hydrodynamic characteristics of a stepped planning hull in the towing tank and the resistance performances of the hull are introduced in this report.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.77-83
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• 2009

In this study, we conducted resistance and propulsion performance test of ship composed of the Resistance Test, Propeller Open Water Test and Self Propulsion Test using the CFD(Computational Fluid Dynamics). We used commercial RANS(Reynolds Averaged Navier Stokes equation) solver, as a calculating tool. The unstructured grids were used in a bow and stern of ship, having complex shape, for a convenience of generating grids, and the structured grids were adopted in a central hull and rest of hull having a relatively simple shape which is called hybrid grid method. In addition, The sliding mesh method was adopted to rotate a propeller directly in the Propeller Open Water and Self Propulsion Test. The Resistance Test and Self Propulsion Test were calculated using Volume of Fluid (VOF) model and considering a free surface. And all The three cases were applied realizable k-epsilon model as the turbulence model. The results of calculations were verified for the suitability of calculations by comparing MOERI's EFD results.

• Journal of Ocean Engineering and Technology
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• v.28 no.6
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• pp.493-499
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• 2014

The resistance performances were studied for two 50-ft-class power yachts made of carbon fiber reinforced plastic (CFRP) with different hull form characteristics using model tests. The tests were carried out at a high-speed circulating water channel (CWC) for the 16–38 knot range. The total resistance, trim, and sinkage were measured, and the results were compared with wave patterns. The results showed that a chine position at the draft line had a strong effect on the planning performance and resistance performance in a certain velocity range.

• Bulletin of the Society of Naval Architects of Korea
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• v.7 no.2
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• pp.41-60
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• 1970

Despite it's limitations, the existing Stream Line Tracing Method(Inverse Method) can be applied effectively to the design of better hull forms with practical proportions. Most of the calculating mechanism by the method for hull form design has been achieved. In this paper, authors have tried to improve the quality of wave making resistance on the 10,000GT liner among FY'67 Korean Standard Ship Form. Some numerical results obtained in this work and designed new lines are shown.

• Korean Journal of Computational Design and Engineering
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• v.13 no.6
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• pp.440-449
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• 2008

This paper deals with a method calculating various hull form parameters which are required in numerical analysis for ship performance such as motion, maneuverability, resistance and propulsion, etc. After the hull form is designed, before the model tests the ship's performances are evaluated by various analysis tools in which the hull form parameters are used with many kinds of forms aside from offset data. Here, The hull form parameters characterize the properties of hull form and contain positional, differential and integral information implicitly. Generally, the commercial CAD-system has not functions enough for supporting these form parameters and therefore each shipyard uses its own in-house analysis program as well as commercial analysis software. To overcome these limitations, modules for supporting these analysis programs have developed. The modules contain cubic composite spline cure using local curve fairing, intersect algorithm, Gaussian integral, and other geometric techniques needed in calculating hull form parameters. Using our analysis-supporting modules, a complex hull form can be remodeled exactly to the hull form designed by CAD-system and any hull form parameter required in various performance analyses can be calculated.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.150-155
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• 2012

One of the primary purposes of tugs is for the towing of other ships in salvage operations. In order to conduct such a task safely, the tug should be capable of generating the appropriate towing forces. Therefore the prediction of resistance against a towed ship during towing operation is a very important and essential procedure. This paper studies the ship resistance calculation program to predict towing force. The calculation program consists of the functions that calculate basic hull resistance in calm water, added resistance due to wind, drifting, hull roughness, waves, shallow water and currents. All predictions are calculated by statistical and empirical methods by graph or formula. The calculation results made by this program are compared with the results from the U.S. Navy's Towing Manual. These results confirm that this computer program is quite capable of appropriately predicting the resistance of damaged ships.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.3
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• pp.175-181
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• 2021

This study describes the model tests in ice according to the frictional coefficient of an ice-breaking ship and the change in ice resistance by the analysis method for each component of ice resistances. The target vessel is a 90K DWT ice-breaking tanker capable of operating in ARC7 ice conditions in the Arctic Ocean, and twin POD propellers are fitted. The hull was specially painted with four different frictional coefficients on the same ship model. The total ice resistance can be separated by ice breaking, ice buoyancy, ice clearing resistances through the tests in level ice, pre-sawn ice and creep test in pre-sawn ice under sea ice thickness of 1.2 m and 1.7 m. Ice resistance was analyzed by correcting the thickness and bending strength of model ice by the ITTC correction method. As the frictional coefficient between the hull and ice increases, ice buoyancy and clearing resistances increase significantly. When the surface of the hull is rough, it is considered that the broken ice pieces do not slip easily to the side, resulting in an increase in ice buoyancy resistance. Also, the frictional coefficient was found to have a great influence on the ice clearing resistance as the ice thickness became thicker.