• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.1
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• pp.108-117
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• 2024

In this study, simulations based on computational fluid dynamics were performed for self-propulsion performance prediction of a catamaran that has asymmetrical inside and outside hull form and numerous knuckle lines. In the simulations, the Moving Reference Frame (MRF) or Sliding Mesh (SDM) techniques were used, and the rotation angle of the propeller per time step was different to identify the difference using the analysis technique and condition. The propeller rotation angle used in the MRF technique was 1˚ and those used in the SDM technique were 1˚, 5˚, or 10˚. The torque of the propeller was similar in both the techniques; however, the thrust and resistance of the hull were computed lower when the SDM technique was applied than when the MRF technique was applied, and higher as the rotation angle of the propeller per time step in the SDM technique was smaller in the simulations for several revolutions of the propeller to estimate the self-propulsion condition. The revolutions, thrust, and torque of the propeller in the self-propulsion condition obtained using linear interpolation and the delivered power, wake fraction, thrust deduction factor, and revolutions of the propeller obtained using the full-scale prediction method showed the same trend for both the techniques; however, most of the self-propulsion efficiency showed the opposite trend for these techniques. The accuracy of the propeller wake was low in the simulations when the MRF technique was applied, and slight difference existed in the expression of the wake according to the rotation angle of the propeller per time step when the SDM technique was applied.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.945-952
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• 2018

Recently, bass fishing has become a marine leisure sport in Korea. There are 4 major fishing associations in Korea, and each association holds 10-15 tournaments each year. However, supply of 17 ft bass boats, which are preferred in leagues, depends 100 % on imports. In this study, we have derived the main specifications to develop the initial hull forms of a 18.5ft bass boat through statistical analysis based on mothership data. In addition, CFD numerical analysis was carried out according to deadrise angle and longitudinal center of gravity, which strongly influenced the resistance and planing performance. For numerical analysis, design speed was set to $Fn=3.284 (Re=9.858{\times}10^7)$, the deadrise angle was set from 12 to $20^{\circ}$, and the longitudinal center of gravity was set in the range of 0 to $8%L_{wL}$ from the center of buoyancy to the stern. Based on the numerical results, we first set the range of these factors by resistance performance and immersion keel length. Furthermore, using a correlation graph of Savitsky's Drag-Lift ratio, we derived the deadrise angle ($14-16^{\circ}$) and longitudinal center of gravity ($4-6%L_{wL}$).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.2
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• pp.136-151
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• 1984

The purpose of this study is to find out the linkage relationship of the resistance genes Wbph1 and Wbph2 which are known to be present in the rice cultivar N22 and ARC 10239 respectively, with the genetic markers which are identified as the specific linkage tester. Crosses were made between the resistant parents and the genetic marker stocks and their F$_2$ populations were grown out in the field. The genetic segregations of the marker character were studied and the seeds were harvested individual plant base. These F$_3$ seeds were grown into plant-line base in the greenhouse and their responses to the whitebacked planthopper were tested. Then the linkage relationship between the F$_2$ plant marker character and the F$_3$ resistance responses to the whitebacked planthopper were examined. In the F$_2$ generation of the crosses between the resistant parent N22 and the genetic marker stocks, the genetic markers, such as lg, d-t, g, la, bl and gl, showed the segregation of 3 dominance to 1 recessiveness, and the Bh marker segregated into 9:7 ratio. Another 4 marker genes, such as Cl, gh, Lh and bc, did not show the good fittness to the expected value. In the F$_2$ generation of the crosses between the resistant parent ARC 10239 and the genetic marker stocks, the genetic markers, such as Cl, lg, Pn, g, la, bl and gl, showed the segregation of 3 dominance to 1 recessiveness, and the Bh gene segregation fitted well to the 9:7. The rest 4 genetic markers, such as gh, Lh, nl and be, did not show the good fitness to the expected ratio. The resistance genes Wbphl of N22 and the Wbph2 of ARC 10239 appeared to be single dominant gene each. The Wbphl gene was linked with the marker gene, liguleless (lg) of linkage group II with the recombination value of 36.8%, and with the black hull (Bh) with the value of 35.9%. The Wbph2 gene appeared to be independent of all the markers tested here, such as Cl, lg, Pn, g, Lh, la, nl, bl, bc, gl, Bh, of linkage gtoup I, II, III, IV, VI, VII, VIII, IX, X, XI, and XII respectively. That the Wbph2 linkage relations were not investigated was regarded as the causes that the tested marker genes on the chromosome were located with the resistance gene at the distant loci, and of the phenctypic properties of the marker characters. The Wbph2 linkage relations should be reexamined in the cross combinations of linkage group Ⅶ, Ⅷ, Ⅹ and XII including linkage group V which was not tested in this experiment.

• Journal of Ocean Engineering and Technology
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• v.25 no.2
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• pp.55-61
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• 2011

A field trial in an ice-covered sea is one of the most important tasks in the design of icebreaking ships and offshore structures. To correctly estimate the ice load and ice resistance of a ship's hull, it is essential to understand the material properties of sea ice during ice field trials and to use the proper experimental procedure for gathering effective ice data. The first Korean-made icebreaking research vessel, "ARAON," had her second sea ice trial in the Arctic Ocean during the summer season of 2010. This paper describes the test procedures used to obtain proper sea ice data, which provides the basic information for the ship's performance in an ice-covered sea and is used to estimate the correct ice load and ice resistance of the IBRV ARAON. The data gathered from the sea ice in the Chukchi Sea and Beaufort Sea during the Arctic voyage of the ARAON includes the temperature, density, and salinity of the sea ice, which was believed to be from two-year old ice floes. This paper analyses the gathered sea ice data in comparison with data from the first voyage of the ARAON during her Antarctic Sea ice trial.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.18-22
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• 2011

The Ranking source panel method was used to predict the flow phenomenon of a ship with a goose-neck type bulbous bow penetrating the free surface. The non-linearity of the free surface boundary condition was fully satisfied using an iterative calculation method, and the raised panel method was adopted to obtain a more stable solution at each iteration step. The panel cutting method was applied to generate a hull calculation grid at each iteration step, including the first step. At that time, the nose of the goose-neck type bulbous bow was divided by the free surface and the free surface panel was modified at each iteration step using the variable free surface panel method. Numerical calculations were performed to investigate the validity and efficiency of the applied numerical algorithm using the 3600 TEU container carrier. The computed wave resistance coefficients were compared with the experimentally achieved residual resistance coefficients.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.576-582
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• 2016

To cope with international regulations, such as Energy Efficiency Design Index (EEDI), Ship Energy Efficiency Management Plan (SEEMP) and so forth, and to enforce limitations on $CO_2$ emissions, green-ship technology to lower fuel consumption has been actively researched, and the development of an energy-saving device (ESD) is being pursued. In order to design an ESD for small and medium-sized domestic vessels, an analysis on flow characteristics has been performed in the present study. Through a model test and numerical analyses, the characteristics of flow around the stern bilge and bulb have been compared to improve wake quality and resistance performance. As a result of these comparisons and analyses, a vertical plate has been adopted,, as a new ESD. Design criteria for the proposed ESD are also suggested. By applying this new ESD, it is expected that the total resistance and average nominal wake can be reduced by 3.04 % and 18.8 %, respectively.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.27-38
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• 1997

This paper is concerned with the calculation of the wave resistance for SWATH ships based on a low order Rankine source panel method. Two types of free surface boundary conditions, Dawson type (double model approximation) and Kelvin type (free stream approximation) are used. For the free surface boundary calculation, an analytic differentiation is employed instead of implementing a finite difference scheme. Then, the radiation condition is satisfied by, so called, the panel shift method. The numerical results using the above two methods are compared with those using the thin ship/modified slender body approximation and also with the experimental results. The SWATH models considered are a single strut SWATH and a twin strut SWATH together with the variations of two demihull separation distance. In order to prove the validity of the program developed, the numerical calculations for a Wigley mono hull and Wigley twin hulls are compared with the available experimental results.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.12-20
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• 1997

A potential-based panel method has been developed to investigate the resistance characteristics of a high speed catamaran advancing on the free surface. Normal dipoles and sources are distributed on the body surface while sources are distributed on the free surface. Linearised free surface conditions are used in the present analysis. To avoid the instabilities due to the velocity difference between inner and outer flow of a high speed catamaran, Kutta condition has been applied at the stern. Model test has been carried out not only to validate the numerical results but to confirm the capabilities of a CWC(Circulating Water Channel). It is believed that we can obtain the qualitatively reasonable results in the CWC. Computed results are compared with those of experiments and Insel's experimental values. Since the Kutta condition is applied at the stern, stable solutions are obtained at the high speed range. The present method, using linearised free surface conditions at the high speed range, seems to be a useful tool in the hull form design of a high speed catamaran.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.1
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• pp.78-85
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• 2014

LNG-RV has the additional equipments that enable to re-gastify liquefied LNG in LNG carrier. This vessel has Submerged Turret Loading(STL) system which transports gas through submarine terminal. When LNG-RV is operating at sea, the opening condition is formed by detaching STL equipment from a vessel. The primary objective of the current work is to estimate accurate speed loss for the opening condition of the LNG-RV employing numerical calculations and model tests. In the model tests, resistance and self-propulsion tests are carried out for the bare-hull and the opening condition without STL. In addition to these, flow visualization utilizing tuft is used to make the flow patterns visible, in order to get a qualitative or quantitative information for inner part in case of detaching the STL.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.876-883
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• 2016

In this study, we selected CFRP to construct a canoe hull. A ship design was made using a commercial ship design program, SOLIDWORKS, and a flow analysis of the canoe on a free surface was calculated using STAR-CCM+. A flow field and waveform were obtained in this way. These results were used to check the resistant performance of the canoe. Results showed that if the draft is 0.09 m, it is safe to run at less than 4 m/s, and if draft is 0.24 m, it is safe to run at less than 2 m/s. Moreover, it was confirmed that those speeds can be made by two adults. The developed canoe, which is 20 % lighter in comparison with conventional FRP models, was briefly introduced in this paper.