• Journal of the Society of Naval Architects of Korea
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• v.39 no.4
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• pp.60-65
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• 2002

In order to generate hull form, we introduced optimization process. Fairness criteria is applied to object function, B-Spline control vertices are considered as design variables, optimization is proceeded with satisfying geometric constraint conditions. GA(Genetic Algorithm) and optimality criteria are applied to optimization process in this study.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.4
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• pp.21-28
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• 1984

As a way of overcoming or improving the great depression in he world shipping and shipbuilding industries, a great effort has been made on the development of fuel-economic hull forms. Recently, the author(s) had presented part of the results of his study on this subject(full slow speed ships) in PRADS 83, and are presently carrying out the research program on the same subject for fine fast speed ships. This paper is the introduction and summary of the basic concept and mathematical treatment applied in this research.

• Journal of Ocean Engineering and Technology
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• v.21 no.5
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• pp.47-54
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• 2007

Ship structures are subject to severe environmental loads causing appreciable hull girder deflection which in turn affects the piping system attached to the main hull in the form of displacement load. While this load may cause failure in the pipes, loops have been widely adopted as a measure of preventing this failure with the idea that they may lower the stress level in a pipe by absorbing some portion of the displacement load. But as the loops also have some negative effects such as causing extra manufacture cost, deteriorating the function of the pipe and occupying extra space, the number and the dimensions of the loops adopted need to be minimized. This research develops a design formula for pipe loops. The accuracy of the proposed design formula was verified by comparing two results respectively obtained by the proposed formula and MSC/NASTRAN. The paper ends with the sample example showing the efficiency of the proposed formula.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.42-47
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• 2011

In this paper, wake equalizing duct (WED) form optimization was carried out using computational fluid dynamics (CFD) techniques. A WED is a ring-shaped flow vane with a foil-type cross-section fitted to a hull in front of the upper propeller area. The main advantage of a WED is the power savings resulting from the uniformity of the velocity distribution on the propeller plane, a reduction in the flow separation at the aft-body, and lift generation with a forward force component on the foil section. This paper intends to evaluate these functions and find an optimized WED form for minimizing the viscous resistance and equalizing the wake distribution. In the optimization process, the study uses four WED parameters: the angle of the section, longitudinal location, and angles of the axes for the half rings against the longitudinal and transverse planes of the ship. KRISO 300K VLCC2 (KVLCC2) is chosen as an example ship to demonstrate the WED optimization. The optimization procedure uses genetic algorithms (GAs), a gradient-based optimizer for the refinement of the solution, and Non-dominated Sorting GA-II(NSGA-II) for Multiobjective Optimization. The results show that the optimized WED can reduce the viscous resistance at the expense of the uniformity of the wake distribution.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.6
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• pp.471-477
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• 2015

When a ship sails in a seaway, the resistance on a ship increases due to incident waves and winds. The magnitude of added resistance amounts to about 15–30% of a calm-water resistance. An accurate prediction of added resistance in waves, therefore, is essential to evaluate the performance of a ship in a real sea state and to design an optimum hull form from the viewpoint of the International Maritime Organization (IMO) regulations such as Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI). The present study considers added resistance problem of AFRAMAX-class tankers with the conventional bow and Ax-bow shapes. Added resistance due to waves is successfully calculated using 1) a three-dimensional time-domain seakeeping computations based on a Rankine panel method (three-dimensional panel) and 2) a commercial CFD program (STAR-CCM+). In the hydrodynamic computations of a three-dimensional panel method, geometric nonlinearity is accounted for in Froude-Krylov and restoring forces using simple wave corrections over exact wet hull surface of the tankers. Furthermore, a CFD program is applied by performing fully nonlinear computation without using an analytical formula for added resistance or empirical values for the viscous effect. Numerical computations are validated through four degree-of-freedom model-scale seakeeping experiments in regular head waves at the deep towing tank of Hyundai Heavy Industries.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.10a
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• pp.241-242
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• 2009

There are marry ships and marine structures and also has marry differences on according to the shape and the interval of hulls to the purpose. the multi-submerged body needs appropriate distance between the hulls because of the optimum hull form. thus, through this paper, the flow characteristics behind the multi-submerged body according os the distance ration between the hulls and various angles of attack was conducted.

• Horticultural Science & Technology
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• v.33 no.4
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• pp.518-524
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• 2015

The objective of this research was to investigate the influence of various depths of expanded rice hull (ERH) medium and fixation dates of runner plantlets of 'Seolhyang' strawberry on the growths in nursery field and in plastic house soil after transplanting. The five treatments in medium depths (30, 50, 70, 90, and 110 mm) and four treatments in fixation dates (1st and 15th July and 1st and 15th August) were tested. The growths of runner plantlets were investigated before transplanting to plastic house soil. The early growth and inflorescence rates of crops after transplant to plastic house soil were also investigated. The plant height and fresh weight of runner plantlets were the highest in the medium depths of 50, 70, and 90 mm. The medium depth of 30 mm had higher numbers of first roots, but lower root fresh weight compared to those of 70, 90, and 110 mm. The treatment of 30 mm in medium depth showed poorer growth in all indexes except root length and root weight compared to those of 70, 90, and 110 mm. The runner plantlets fixed on July 1 and July 15 showed good root growth and the weights of ERH adhered to form root balls were 18.3 g and 13.9 g, respectively. The detached amount of ERH was less than 40% in the two treatments when root balls were shaken by a vibratory sieve shaker. The plant growth at 45 days after transplanting to plastic house soil were not significantly different when the runner plantlets were fixed in the period from July 1 to Aug. 1. The inflorescence rates of the first cluster were 93 to 100% when runner plantlets were fixed in the period from July 1 to Aug. 1. By contrast the runner plantlets fixed on the Aug. 15 had a 67% in florescence rate for the first cluster. These results indicate that optimum depth of ERH medium was 7 cm and the ranges of optimum fixation dates are from July 20 to 25.