• 한국해양공학회지
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• 제20권3호
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• pp.1-6
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• 2006

Modulation theory describes propagation of surface waves with deep wave number and frequency modulation. Locally spectrally narrow wave packet can have accumulated large scale frequency shift of carrier wave during propagation. Some important nonlinear modulation effects, such as negative frequencies, phase kinks, crest pairing, etc., often observed experimentally at long fetch propagation of finite amplitude surface wave trains, are reproduced by the proposed theory. The presented model permits also to analyze the appropriately short surface wave packets and modulation periods. Solutions show the wave phase kinks to arise on areas' of relatively small free surface displacement in complete accordance with the experiments.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 2004년도 학술발표논문집 Proceedings of Coastal and Ocean Engineering in Korea
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• pp.128-137
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• 2004

• 대한조선학회논문집
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• 제50권1호
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• pp.49-58
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• 2013

Recently, the design of commercial ships with less green-house gas is one of great interests in naval architecture fields. Ship designers are asked to find optimum hull forms with minimum resistance in ocean waves. The accurate computation of added resistance, therefore, is getting more important for the prediction of power increase in random ocean waves. This study focuses on the numerical computation of added resistance on ships with Ax-bow shapes which are designed to reduce added resistance. To this end, the time-domain Rankine panel methods based on weakly-nonlinear and weak-scatterer approaches are applied, which can reflect the influence of above-still-water bow shape. As computational models, KCS and KVLCC2 hull forms are considered. Each ship is combined with the three types of Ax-bow shape, and computational results are compared each other.

• 한국해안해양공학회지
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• 제19권3호
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• pp.222-227
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• 2007

심해에서 생성된 최극해파가 파랑과 상호작용하는 현상에 대한 연구를 수행하였다. 이러한 파랑은 분산집중을 이용하여 산정하였다. 이러한 과정은 선형 및 비선형 방정식의 해를 구하여 얻을 수 있다. 상호작용에서 비선형성의 역할을 강조하였다.

• 한국해양공학회지
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• 제18권2호
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• pp.18-24
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• 2004

In this study, the Mild slope equation is extended to both rapidly varying topography and nonlinear waves, using the Hamiltonian principle. It is shown that this equation is equivalent to the modified mild-slope equation (Kirby and Misra, 1998) for small amplitude wave, and it is the same form with the nonlinear mild-slope equation (Isobe, 1994) for slowly varying bottom topography. Comparing its numerical solutions with the results of some hydraulic experiments, there is good agreement between them.

• Journal of Ship and Ocean Technology
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• 제7권3호
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• pp.1-12
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• 2003

The influence of nonlinear phenomena on the behavior of stationary forced flexural-gravity waves on the surface of deep water is investigated, when the perturbation of external pressure moves with near-resonant velocity. It is shown that there are three branches of bounded stationary solutions turning into asymptotic solutions of the linear problem with zero initial conditions. For the first time ice sheet destruction by turbulent fluctuations of atmosphere pressure in ice adjacent layer in wind conditions is studied.

• 대한조선학회논문집
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• 제51권6호
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• pp.459-479
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• 2014

This paper considers experimental and numerical studies on added resistance in waves. As the numerical methods, three different methods, strip method, Rankine panel method and Cartesian-grid method, are applied. The computational results of vertical motion response and added resistance are compared with the experimental data of Series 60($C_B=0.8$) hull, S175 containership and KVLCC2 hull. To investigate the influence of above-still water hull form, a Rankine panel method is extended to two nonlinear methods: weakly-nonlinear and weak-scatterer approaches. As nonlinear computational models, three ships are considered: original KVLCC2 hull, 'Ax-bow' and 'Leadge-bow' hulls. Two of the three models are modified hull forms of original KVLCC2 hull, aiming the reduction of added resistance. The nonlinear computational results are compared with linear results, and the improvement of computational result is discussed. As experimental approach, a series of towing-tank experiment for ship motions and added resistance on the three models (original KVLCC2 hull, 'Ax-bow' and 'Leadge-bow') are carried out. For the original KVLCC2 hull, uncertainty analysis in the measurement of vertical motion response and added resistance is performed in three waves conditions: ${\lambda}/L=0.5$, 1.1, 2.0. From the experimental results, the effects of hull form on added resistance are discussed.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.364-367
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• 2006

Nonlinear internal waves (NLIWs) are usually generated by nonlinear process on linear internal waves (IW). Near HengChun Ridge that links Taiwan and Luzon Islands, we found that there are linear internal waves following NLIW and they travel westward at different speed, about 1.5 m/s for IW and 2.9 m/s for NLIW. This phenomenon was observed on site with ship radar and echo sounders, and later verified with thermistor chain. West of Luzon Strait, the separation of NLIW are 5 km or more, while linear internal waves are lines of wave crests at nearly equal distance that is only a few hundred meters apart. The current hypothesis is that most of the energy of internal tide forms a beam that propagates upward from the eastern shoulder of ocean ridge and later interacts with sea surface and thermocline. The interaction with thermocline generates linear internal wave that propagate along the pycnocline at about 1.5 m/s. The interaction with sea surface scatters internal wave energy downward, ensonifies the water column and generates large nonlinear waves that propagate westward at 2.9 m/s as mode 1 in a waveguide.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.243-249
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• 2003

The head-on collision of two solitary waves are examined using a boundary element method. Attachment, detachment times and alplitudes and maximum run-up times and amplitudes are computed. Consolidation times show local minimum value if two waves are of equal amplitudes are colliding. Attachment times show local maximum value if the amplitudes of two waves are the same. The detachment time show local maximum if two wves are the same. The detachment amplitude show local minimum values if the amplitude e(=a/h) is greater than 0.3.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.526-544
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• 2021

Based on the potential flow theory, a fully nonlinear numerical procedure is developed with boundary element method to analyze the interaction between a fixed semi-submersible platform and incident waves in open water. The incident wave is separated from the scattered wave under fully nonlinear boundary conditions. The mixed Euler-Lagrangian method is used to capture the position of the disturbed wave surface in local coordinate systems. The wave forces exerted on an inverted conical frustum are used to ensure the accuracy of the present method and good agreements with published results are obtained. The hydrodynamic characteristics of the semi-submersible platform interacting with regular waves are analyzed. Pressure distribution with time and space, tension and compression of the platform under wave action are investigated. 3D behaviors of wave run-ups are predicted. Strong nonlinear phenomena such as wave upwelling and wave interference are observed and analyzed.