• Composites Research
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• v.34 no.6
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• pp.350-356
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• 2021

When a ship with a planing line operates or turns in a straight line, the floating position and trim change according to the speed, and a large resistance is generated on the hull. In this paper, the resistance to a planing line was estimated through the computational fluid dynamics of a leisure boat with improved hull weight and durability by applying a carbon composite material to the hull. The resistance performance of the bow and stern of the 18ft class leisure boat was checked and the flow field of the entire vessel was estimated, and the stability of the planing line was confirmed by comparing the resistance of each trim through numerical analysis. In addition, it was confirmed that the designed planing line could withstand it sufficiently because the force applied to the hull was not large, and The stability of the boat was analyzed by calculating the wavelength of the wave and the length of the ship as the ratio of gravity to the inertial force and checking how much force the rolling occurred.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.1-14
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• 1996

Especially in the case of a full form ship, the stability on course can be considered to become severest among 4 items of criteria in Interim Standards for Ship Maneuverability adopted by IMO in 1993. The purpose of this study is to find some ideas for the improvement of stability on course through changes in rudder area with reference to span distance. In this paper, we established the formula on the relation between the experimental constants relevant to rudder normal force and hydrodynamic derivatives of hull-propeller-rudder system. We carried out various kinds of captive model test relevant to rudder normal force etc., and evaluated hydrodynamic derivatives of hull-propeller-rudder system, and analyzed the stability on course with the parameter of changes in rudder area. Furthermore, we also discussed effects of changes in rudder area on maneuvering performance including stability on course, based on computer simulation. As a result, it is clarified that there is a possibility that stability on course may become bad through an increase of rudder area. The reason for the bad stability on course is that the void space between the upper edge of rudder and the lower part of stern overhang decreases. This space change exerts a great influence on straightening coefficient of incoming flow to rudder in maneuvering motion, which has close relation to stability on course.

• 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 ($4-6%L_{wL}$).

• Journal of the Korean Chemical Society
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• v.33 no.1
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• pp.97-105
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• 1989

This study deals with micellar effects on hydrolyses of p-nitrophenyl carboxylic esters(p-NPCE) mediated by 2-alkylbenzimidazole(R-BI) and sodium 2-alkylbenzimidazole-5-sulfonate(R-BISO$_3$Na) in aqueous and CTABr solutions. The reactions mediated by R-BI and R-BISO$_3$Na in micellar solutions are obviously slower than those by benzimidazole(BI) and sodium benzimidazole-5-sulfonate(BISO$_3$Na) respectively, and the reaction rates were decreased with increase of lengths of alkyl groups. This prestents a striking contrast to the reactions in aqueous solutions without added CTABr, of which the reaction rates are on approximately same levels. It seems due to steric effect of alkyl groups for R-BI and R-BISO$_3$Na in the Stern layer of micelle, and it is supported by measured activation parameters(${\Delta}H^{\neq},\;{\Delta}G^{\neq}\;and\;{\Delta}S^{\neq}$) of the reactions in aqueous and micellar solutions. In addition to nucleophilic ability of benzimidazole(BI) moiety of R-BISO$_3$Na on the reactions, these compounds with long alkyl groups(nonyl to pentadecyl) which form a micelle of themselves increase the reaction rates due to their micellar catalyses in aqueous solutions, not including CTABr. We measured the isotope effects to elucidate the mechanism of hydrolyses of p-nitrophenyl carboxylic esters, and the relative first order rate constant($k'_{H_2O}/k'_{D_2O}$) are on range of 2.5∼3.2. This range is too high to conclude that the hydrolyses of p-NPA mediated by various R-BISO$_3$Na proceed by nucleophilic mechanism. In other words, the reactions are assumed to proceed in part by general basic one, as compared with the reaction catalyzed by imidazole(IM) in aqueous solution.