• International Journal of Naval Architecture and Ocean Engineering
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• 제4권1호
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• pp.44-56
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• 2012

Autonomous Underwater Vehicles (AUVs) provide a useful means of collecting detailed oceano-graphic information. The hull resistance of an AUV is an important factor in determining the power requirements and range of the vehicle. This paper describes a procedure using Computational Fluid Dynamics (CFD) for determining the hull resistance of an AUV under development, for a given propeller rotation speed and within a given range of AUV velocities. The CFD analysis results reveal the distribution of the hydrodynamic values (velocity, pressure, etc.) around the AUV hull and its ducted propeller. The paper then proceeds to present a methodology for optimizing the AUV profile in order to reduce the total resistance. This paper demonstrates that shape optimization of conceptual designs is possible using the commercial CFD package contained in Ansys$^{TM}$. The optimum design to minimize the drag force of the AUV was identified for a given object function and a set of constrained design parameters.

• 한국해양공학회지
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• 제34권6호
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• pp.377-386
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• 2020

This paper discusses the effectiveness of onboard measurements and data extracted from weather information for speed-power analysis. Furthermore, validation results of hull and propeller cleaning and painting during dry-docking are discussed. Wind and wave information can be obtained from onboard measurements or weather information from the National Oceanic and Atmospheric Administration (NOAA). The weather information of a specified position and time is extracted from NOAA weather data and compared with onboard measurements. In addition, to validate the effects of hull cleaning and painting during dry-docking, speed-power analysis results of before and after dry-docking are compared. The results show that both onboard measurements and weather information show acceptable reliability when added resistance and speed-power analysis results are compared with each other. Moreover, the ship performance analysis (SPA) software clearly shows the effects of hull cleaning and painting, and it can provide reliable analysis results with either onboard measurements or weather information. In conclusion, it is confirmed that the analysis method and SPA software used in this study are effective in analyzing the ship's speed-power performance.

• 한국기계연구소 소보
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• 통권9호
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• pp.169-181
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• 1982

This paper presents three methods for ship hull form improvement on the basis of wave pattern analysis. These methods are primarily based on the assumption that a linear relation exists between the small difference of hull sections and the difference of the wave amplitude functions. The improved hull form of ship is made by superposing a thin hull form on that of a parent model. The first method use the simplification of framelines and Michell's Theory to the formula of wave resistance for superposed thin ship. The second method use tent functions and Michell's Theory to that. And the third is experimental method.

• 대한조선학회논문집
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• 제45권3호
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• pp.337-343
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• 2008

There are various hull types on the mid-size superyachts around $30\;{\sim}\;45m$. In any case, it is important to design the proper hull shape in viewpoint of the reduction of wave resistance, because small vessels such as superyachts are running at relatively higher Froude Number than other merchant ships. FLUENT with a VOF option was employed to investigate the flow fields around the superyachts having three-typical hull types: U-, V-types and catamaran. Overall performances including free surface flow were compared to figure out hydrodynamic characteristics of superyachy by numerical simulation.

• 한국해양공학회지
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• 제15권1호
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• pp.1-6
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• 2001

This study focuses on the potential flow analysis for a hull with the transom stern. The method is based on a low order panel method. The Kelvin type free-surface boundary condition which is known to better fit experimental data for a high speed is applied. To treat a dry transom stern effect a special treatment for the free-surface boundary condition is adopted at the free-surface region after the transom stern. Trim and sinkage, which are important in high speed ships, are considered by an iterative method. Pressure and momentum approaches are used to calculate the wave resistance. Numerical calculations are performed for Athena hull and these results are compared with the experimental data and also other computational results.

• Journal of Advanced Marine Engineering and Technology
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• 제35권8호
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• pp.1117-1123
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• 2011

비접지 배전방식이 채택되는 선박은 일선지락 상황에서도 정전사고로 이어지지 않으므로 상대적으로 안정적인 급전이 가능하다. 그러나 비접지 계통에서 발생하는 지락고장은 대지 전압을 왜곡시켜 선체에 대한 선로 전압을 상승시키므로 감전사고와 전기화재의 위험이 높아진다. 특히 선로와 선체 간에 작용하는 분포용량은 대지임피던스의 한 요소로서 지락고장 시 대지전압의 왜곡 특성에 큰 영향을 미친다. 이 같은 대지전압의 변화는 3상 대지전압 중성점의 이동에 의해 설명될 수 있다는 점에서 본 연구에서는 대지임피던스를 입력으로 할 때 대지전압을 출력으로 하는 연산모듈을 구성한 후 이를 이용하여 접지저항 변화에 대응하는 대지전압 중성점의 이동 경로 특성을 확인하였다. 또한 다양한 조건에서 나타나는 중성점 이동경로를 구하는 한편 실제 배전계통에서의 측정 결과와 비교함으로써 제시된 분석방법의 적정성을 나타내었다.

• 해양환경안전학회지
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• 제23권4호
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• pp.432-438
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• 2017

본 연구의 주목적은 기존선형을 바탕으로 연료 절감이 가능한 표준화된 개조선형을 개발하는 것이다. 설계 흘수와 설계 선속을 고려하여 대상선박의 선수부 형상을 검토하였다. 실제 운항 상태 별로 대상선박에 대하여 저항성능을 평가하였다. 상용 전산유체역학(CFD) 코드와 수조 모형시험 자료는 유효마력 평가를 위해 사용되었다. 실제 운항 상태를 고려하여 최소저항을 가지는 3가지 개조선형을 제시하였다. 제시된 개조선형은 고객이 선택가능 하다는 점에서 고객 맞춤형 기성품 선형이라고 명하였다. 개조선형 별로 실제 운항 상태에 따라 유효마력을 추정하였다. 가장 낮은 흘수에서 운항할 경우, 기존선형과 비교하여 볼 때 개조3 선형의 저항성능은 저속영역인 16~18노트에서 약 11~16 %로 향상된 결과를 보여 주었다. 중간 흘수인 8.3m에서 운항할 경우, 개조3 선형의 저항성능은 저속영역에서 기존선형보다 약 6~11 %로 향상된 결과를 보여 주었다. 가장 높은 흘수인 9.5m에서 운항할 경우, 모든 선형의 저항성능은 저속영역에서 큰 차이를 보이지 않았다.

• 수산해양기술연구
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• 제35권3호
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• pp.335-342
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• 1999

The purpose of present research is to develop and efficient numerical method for the calculation of potential flow and predict the wave-making resistance for the application to ship design of tuna purse seiner. Havelock was considered the wave resistance of a post extending vertically downwards through the water from the surface, its section by a horizontal plane being the same at all depths and having its breadth small compared with its length. This enables us to elucidate certain points of interest in ship resistance. However, the ship has not infinite draft. So, the problem which is investigated ind detail in this paper is the wave resistance of a mathematical quadratic model in a uniform stream. The paper deals with the numerical calculation of potential flow around the series 60 with forward velocity by the new slender ship theory. This new slender ship theory is based on the asymptotic expression of the Kelvin-source, distributed over the small matrix at each transverse section so as to satisfy the approximate hull boundary condition due to the assumption of slender body. The numerical results using the panel shift method and finite difference method are compared with the experimental results for wigley mono hull. There are no differences in the wave resistance. However, it costs much time to compute not only wave resistance but also wave pattern over some range of Froude numbers. More improvements are strongly desired in the numerical procedure.

• 한국해양환경ㆍ에너지학회지
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• 제17권3호
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• pp.198-204
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• 2014

바다를 항해하는 선박은 수면 상부 선체가 공기저항을 받게 된다. 이 공기저항은 수면 상부 선체의 형상, 선속, 풍속 그리고 풍향의 영향을 받는다. 공기저항을 추정하는 실험적인 또는 통계적인 방법은 사고 선박의 예인력을 계산하는 중요한 절차 가운데 하나이다. 본 논문에서는 수면 상부 선체의 투영면적과 선속과 풍속과 풍향을 변수로 사용하여, 실험 또는 통계 분석 방법으로 공기저항을 간편하게 추정하는 방법을 보여주었다. 이 방법들은 기존의 사고선박 예인력 추정을 위한 전산 프로그램에 적용하였다.

• 대한조선학회논문집
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• 제57권5호
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• pp.278-286
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• 2020

Reynolds-averaged Navier-Stokes simulations have been performed to investigate an effect of numerical region with high resolution for Kelvin wave around KRISO container ship on its resistance. In the present study, 13 millions cells were used to describe wave profile along the ship hull and Kelvin wave patterns. In order to control a size of numerical region with high resolution for waves around the hull, we employed relaxation zones from a side boundary of numerical domain in which Kelvin wave was suppressed. When the far-field Kelvin wave was not precisely resolved due to the relaxation zone, the instantaneous history of ship resistance was affected although the time average of ship resistance showed -1.15~2.1 % errors. Especially, the damping characteristics of ship resistance in time history was significant when using a large relaxation zone in the side boundary.