• Ocean Systems Engineering
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• 제13권3호
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• pp.225-245
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• 2023

In the present paper, a numerical and experimental analysis for a wave energy converter under extreme environmental conditions is carried out. After the definition of design waves, including a 100-year return period stochastic sea state and a deterministic rogue wave condition, a numerical analysis using potential theory and a RANS equations solver are compared with experiments carried out at the Seakeeping Basin at the Technical University of Berlin. Results are discussed with special emphasis on the limits of potential theory methods for the evaluation of extreme wave conditions and the use of the presented methodology for early design stages.

• 해양환경안전학회지
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• 제18권5호
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• pp.439-445
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• 2012

모래운반선은 호퍼도어를 갖는 경우 제한된 범위내에서 창구덮개의 설치를 면제 받을 수 있으나, 현재 국내에는 호퍼도어를 갖고 있는 선박이 단 한척도 없어 창구덮개를 면제받는 선박이 없는 실정이다. 따라서 모래운반선의 창구덮개 관련 현행 규정의 검토와 사고사례 조사 그리고 현재 운항하고 있는 모래운반선에 대한 설비현황, 복원성능 및 내항성능 평가를 통하여 모래운반선에 대한 창구덮개 면제 조건을 검토하였다. 그 결과, 모래운반선의 경우 창구덮개를 면제 받기 위해서는 화물창의 크기를 조정하여 모래를 화물창 상단부까지 가득 싣더라도 흘수가 만재흘수선을 넘지 않도록 하고, 적절한 풍우밀 조치를 취함으로써 충분한 예비 부력과 복원력 확보가 요구된다. 또한, 배수펌프의 용량은 화물창의 액상상태인 모래를 1시간 이내에 소성상태가 될 수 있도록 배수하기에 충분한 용량이어야 하며, 모든 운항상태에서 작동 가능하여야 한다. 본 연구는 모래운반선의 작업 특성상 창구덮개의 설치작업이 현실적으로 상당히 어렵고, 특히 기상악화시 인명사고로 이어질 수 있는 현실적인 문제점을 항해안전과 관련된 시설기준을 보다 강화함으로써 개선한 것이다.

• 한국항해항만학회지
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• 제37권5호
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• pp.481-486
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• 2013

본 연구에서는 18미터급 쌍동형 선형의 선수벌브 유무에 따른 운동응답특성을 선형 스트립이론에 기초한 상용코드(Seakeeper)를 이용하여 추정하였다. 계산조건으로는 ITTC 파스펙트럼에 기초한 뷰포트 풍력계급 3 ($\bar{T}=2.98s$, $H_{1/3}$ =0.6m), 4 ($\bar{T}=3.85s$, $H_{1/3}$ =1m) 및 5 ($\bar{T}=5.44$, $H_{1/3}$ =2m)의 파스펙트럼을 산출하였고, 조우각은 선수파, 선수사파 및 횡파를 적용하여 종동요의 선체운동응답스펙트럼을 해석하였다. 선수벌브가 적용된 쌍동선 선형은 선수파와 선수사파에서 최대 20%의 종동요 응답이 감소하는 효과를 나타냈다.

• 한국해양공학회지
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• 제30권6호
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• pp.451-457
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• 2016

For a carferry with a displacement of 1,633 tonf, a seakeeping analysis-based direct load approach (DLA) was used in Part I of these series, where the final deliverable was the long-term probabilistic acceleration components. In Part II of these series, the tangential acceleration components are explained based on two approaches: a standard called the IMO CSS code and simple formulas with the probable maximum roll and pitch rotations. The subsequent tangential acceleration-induced external force components are also introduced for these two approaches. The lashing strength components were selected from the IMO CSS code. It was assumed that two different vehicles (a car and a truck) were stowed at the most distant locations on the main deck to assume the largest tangential acceleration components and were secured with four steel wires with longitudinal and transverse lashing angles of $45^{\circ}$. Four cases were considered, with different methods for predicting the acceleration components and different tools for the external loads and lashing strengths involved: cases Rule-LS (rule-based maximum probable roll and pitch angles for predicting the acceleration components in conjunction with LashingSafety), DLA-LS (seakeeping-based long-term acceleration components with LashingSafety), CSS-LC (IMO CSS code-based acceleration components using LashCon), and CSS-LS (IMO CSS code-based acceleration components using LashingSafety). In terms of the acceleration and external force components, the CSS-LC and CSS-LS results are more than two times the results of Rule-LS. Thus, when the external forces and lashing strengths are evaluated using CSS-LC and CSS-LS, the truck needs more lashing wires, while Rule-LS and DLA-LS predict that the present lashing configuration is on the safe side.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1082-1095
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• 2014

In this paper, a new criterion for the identification of slamming events is formulated. This criterion is based on the analysis of the high-frequency response, expressed in terms of the amidships VBM, which occurs after the slams. For this reason, it is named 'whipping' criterion underlining that is based on the analysis of global effects than on the kinematic description of the impact dynamics that was provided by Ochi criterion. Both the new 'whipping' criterion and the Ochi criterion are presented and compared also with respect to their practical application to the experimental data collected in the seakeeping tests with an elastic segmented model.

• 대한조선학회지
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• 제24권2호
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• pp.36-46
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• 1987

This paper presents the results of seakeeping tests in a container ship model in irregular head waves. A time domain signal generating procedure is devised so that the wave maker behaves in accordance with the specified wave spectrum. The surface elevation of generated waves is measured and analysed to render the recorded wave spectrum for comparison with the specified one. Correction is made to the time domain signal until the differences between the two spectra become negligible. The motion responses and vertical acceleration of the self-propelled ship model are measured and analysed by both the spectral and the double amplitude methods. The two methods give nearly same statistical values. Finally the recorded spectra are compared with those calculated from the frequency domain motion analysis to show the credibility of the experimental results.

• 대한조선학회논문집
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• 제51권5호
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• pp.396-408
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• 2014

In this study, uncertainty analysis based on ITTC(International Towing Tank Conference) Recommended Procedures is carried out in the towing-tank experiment for motion responses and added resistance. The experiment was conducted for KVLCC2 model in head sea condition. The heave, pitch and added resistance were measured in different wave conditions, and the measurement was repeated up to maximum 15 times in each wave condition in order to observe the uncertainty of measured data. The uncertainty analysis was carried out by adopting the ISO-GUM(International Organization for Standardization, Guide to the Expression of Uncertainty in Measurements) method recommended by ITTC. This paper describes the details about the analysis method, uncertainty and the measured uncertainty for each source. The uncertainty analysis results are summarized as a tabular form. To validate the accuracy of the present measurement, the experimental results are compared with the results of numerical computation and other experiment. From the present uncertainty analysis, the main sources of uncertainty are identified, which can be very useful to improve the accuracy for added resistance experiment.

• 한국해안·해양공학회논문집
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• 제28권1호
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• pp.27-33
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• 2016

불규칙 파랑 중에서 직접 예인하는 케이슨의 상판침수에 대한 수치해석을 수행하였다. 패널법을 이용하여 주파수 영역에서의 선형 운동해석을 수행하였고, 통계적 방법을 통해 상판침수를 예측하였다. 시간영역 해석에서는 예인시스템, 환경하중 등을 상세히 구현하여 운동해석을 수행하였고, 상판침수 결과를 주파수 영역에서의 결과와 비교하였다. 또한, 시간 영역 해석에서는 예인선의 수 및 배치에 대한 검토를 수행하여 상판침수 측면에서 예인시스템이 미치는 영향과 운송조건을 고찰하였다.

• 한국해양공학회지
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• 제11권2호
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• pp.91-99
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• 1997

This paper presents theoretical formulations and numerical computations for predicting first-and second-order hydrodynamic force on a ship advvancing in waves. The theoretical formulation leads to linearized radiation and diffration problems solving the three-dimensional Green function integral equations over the mean wetted body surface. Green function representing a translating and pulsating source potantial for infinite water depth is used. In order to solve integral equations for three dimentional flows using Green function efficiently, the Hoff's method is adopted for numerical calculation of the Green function. Based on the first-order solution, the mean seconder-order forces and moments are obtained by directly integrating second-order pressure over the mean wetted body surface. The calculated items are carried out for analyzing the seakeeping characteristics of Series 60. The calculated items are hydrodynamic coefficients, wave exciting forces, frequency response functions and addd resistance in waves.

• Ocean Systems Engineering
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• 제5권2호
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• pp.91-107
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• 2015

Ship hull optimization is categorized as a bound, multi variable, multi objective problem with nonlinear constraints. In such analysis, where the objective function representing the performance of the ship generally requires computationally involved hydrodynamic interaction evaluation methods, the objective functions are not smooth. Hence, the evolutionary techniques to attain the optimum hull forms is considered as the most practical strategy. In this study, a parametric ship hull form represented by B-Spline curves is optimized for multiple performance criteria using Genetic Algorithm. The methodology applied to automate the hull form generation, selection of optimization solvers and hydrodynamic parameter calculation for objective function and constraint definition are discussed here.