• 대한조선학회논문집
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• 제46권4호
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• pp.373-381
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• 2009

The running attitude of a high-speed planing craft may change significantly depending on its speed in seaway. Other variables that may influence its running attitude are its weight, center of gravity, sea conditions, and so on. In this paper, planing craft model tests were carried out with respect to above variables in SNU towing tank, and vertical motion responses of a planing craft in regular head waves were analyzed. The experimental results in regular waves were compared with those in calm water, and compared with the theoretical estimations. Finally, the effects of running speeds of a planing craft on its motion amplitudes are confirmed.

• 한국해안·해양공학회논문집
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• 제27권4호
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• pp.258-265
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• 2015

지난 20년 동안 해양구조물과 선박 등에 예상치 못한 피해를 주는 freak waves에 대한 연구자들의 관심이 증가하고 있다. 다양한 연구결과에도 불구하고 아직 freak waves의 발생원인, 발생 메커니즘, 발생확률 등에 대한 상반된 결과로 인해 합의된 결과가 도출되지 못하고 있다. 본 논문에서는 동해항 전면 해상에서 측정된 파랑자료를 분석하여 freak waves에 대한 발생확률을 추정하였다. 유의파고 2.5 m 보다 크고 $H_m/H_S{\geq}2$인 freak waves 3개를 발견하였다. Freak waves의 발생확률은 극치파고분포함수를 사용하여 추정하기 적절하며, Mori, Rayleigh, 그리고 Ahn의 극치파고분포함수는 freak wave의 발생확률을 각각 약 O($10^{-1}$), O($10^{-2}$), 그리고 O($10^{-3}$) 정도로 추정하였다. 본 논문에서 분석된 파랑자료의 freak waves의 발생확률은 O($10^{-2}$)와 O($10^{-3}$) 사이에 위치하였다. 즉, Rayleigh와 Ahn의 극치파고분포함수에 의해 예측된 발생확률의 중간에 위치하였다. 현재 Rayleigh와 Ahn의 극치파고분포함수 중에 어떤 분포함수가 정확한지에 대한 판단은 좀 더 다양한 해역에서의 freak waves의 발생확률에 대한 분석이 필요하다고 판단된다.

• 한국해안·해양공학회논문집
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• 제32권3호
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• pp.161-169
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• 2020

테트라포드로 피복된 경사식방파제 상부구조물에 파가 경사 입사할 때의 파력 변화를 관찰하기 위한 수리모형실험을 수행하였다. 입사파향은 0, 15, 30, 45° 4가지로 변화시켰으며 상부구조물 전면 및 하부면에 파압계를 부착하여 수평 및 연직파력을 계측하였다. 실험을 통해 입사각과 구조물 전면이 이루는 각도가 증가할수록 수평 및 연직 파력이 모두 감소함을 확인하였다. 실험자료 분석 결과로부터 입사파향에 대한 수평 및 연직 파력 감소율 산정식을 각각 제시하였다.

• 한국해양공학회지
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• 제34권4호
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• pp.245-252
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• 2020

Wave run-up is an important phenomenon that should be considered in ocean structure design. In this study, the wave run-up of a surface-piercing circular cylinder was calculated in the time domain using the three-dimensional linear and fully nonlinear numerical wave tank (NWT) techniques. The NWT was based on the boundary element method and the mixed Eulerian and Lagrangian method. Stokes second-order waves were applied to evaluate the effect of the nonlinear waves on wave run-up, and an artificial damping zone was adopted to reduce the amount of reflected and re-reflected waves from the sidewall of the NWT. Parametric studies were conducted to determine the effect of wavelength, wave steepness, and the draft of the cylinder on the wave run-up of the cylinder. The maximum wave run-up value occurred at 0°, which was in front of the cylinder, and the minimum value occurred near the circumferential angle of 135°. As the diffraction parameter increased, the wave run-up increased up to 1.7 times the wave height. Furthermore, the wave run-up was 4% higher than the linear wave when the wave steepness was 1/35. In particular, the crest height of the wave run-up increased by 8%.

• 대한조선학회논문집
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• 제52권4호
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• pp.338-348
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• 2015

In this study, the added resistance of ships in short waves is systematically studied by using two different numerical methods - Rankine panel method and Cartesian grid method – and existing asymptotic and empirical formulae. Analysis of added resistance in short waves has been preconceived as a shortcoming of numerical computation. This study aims to observe such preconception by comparing the computational results, particularly based on two representative three-dimensional methods, and with the existing formulae and experimental data. In the Rankine panel method, a near-field method based on direct pressure integration is adopted. In the Cartesian grid method, the wave-body interaction problem is considered as a multiphase problem, and volume fraction functions are defined in order to identify each phase in a Cartesian grid. The computational results of added resistance in short waves using the two methods are systematically compared with experimental data for several ship models, including S175 containership, KVLCC2 and Series 60 hulls (C_B = 0.7, 0.8). The present study includes the comparison with the established asymptotic and empirical formulae in short waves.

• 대한조선학회논문집
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• 제55권2호
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• pp.103-115
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• 2018

This paper performs a numerical computation of ship maneuvering performance in waves. For this purpose, modular-type model (MMG (Mathematical Modeling Group) model) is adopted for maneuvering simulation and wave drift force is included in the equation of maneuvering motion. In order to compute wave drift force, two different seakeeping programs are used: AdFLOW based on Wave Green function method and SWAN based on Rankine panel method. When wave drift force is calculated using SWAN program, not only ship forward speed but also ship lateral speed are considered. By doing this, effects of lateral speed on wave drift force and maneuvering performance in waves are confirmed. The developed method is validated by comparing turning test results in regular waves with existing experimental data. Sensitivities of wave drift force on maneuvering performance are, also, checked.

• 한국항해항만학회지
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• 제41권5호
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• pp.329-336
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• 2017

This study suggests a general process of analyzing the mooring and cargo handling limit waves, which is an incident to the new energy port under long wave agitation. To reduce damages of ships and harbor structures due to strong wave responses, it is necessary to predict the change of wave field in the mooring berth to make the proper decision by dock master. The berthing area at a new LNG port in the east coast of Korea in this study is frequently affected by oscillations from waves of 8.5~13s periods in the wintertime. The long period waves give difficulties on port operation by lowering the annual berthing ratio. It needs to find the event waves from the real time offshore wave records, which cause over the mooring limits. For that purpose, the wave records from field measurement and offshore wave buoy were analyzed. From numerical simulation, the response characteristics of long period waves in the berthing area were deduced with or without breakwater expansion plan, analyzing the offshore field wave data collected for two years. Some event wave cases caused over the cargo handling and mooring limits as per the standard Korean port design guideline, and those were used for the decision of port operation by dock master, comparing with the real time offshore wave observations.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1995년도 정기학술강연회 발표논문 초록집
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• pp.75-80
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• 1995

The model for the combined refraction and diffraction of water waves, the so-called mild-slope equation, was first developed by Berkhoff (1972) and has been studied by many coastal engineers because the model is able to consider the combined effect of refraction and diffraction of water waves and eliminate the problem of ray crossing which may happen in the previously developed ray theory. (omitted)

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1997년도 정기학술강연회 발표논문 초록집 Annual Meeting of Korean Society of Coastal and Ocean Engineers
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• pp.39-44
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• 1997

As wind waves generated in deep water approach nearshore zone, they experience various physical phenomena caused by bathymetric variations, nonlinear interactions among different wave components and interferences with man-made coastal structures. Among these, the bathymetric variations may play a significant role in the change of wave climate. The accurate calculation of reflection and transmission coefficients of incident waves over a bottom topography is indispensible for the proper and economical design of coastal structures. (omitted)

• 대한조선학회지
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• 제17권2호
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• pp.43-47
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• 1980

In this note the characteristics of ocean waves is reviewed from standpoint of practical application. To describe the ocean wave in mathematical terms many wave theories have been developed, each under some different aspects. Among well-established wave theories the gravity wave theory and the cnoidal wave theory are examined by a mathematical principle. Finally valid range of each theory is suggested for its numerical evaluation.