• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.172-178
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• 2003

As a typoon gets into harbour, a moored ships shows erratic motions and even mooring line failures is occurred. Such troubles may be caused by harbour resonance phenomena, result in large motion amplitudes at law frequency, which is closed to the natural frequency of the moored ship. The nonlinear motions of a moored ship beside quay are simulated under external forces due to wave, current including mooring forces in time domain. The forces due to waves are obtained from source and dipole distribution method in the frequency domain. The current forces are calculated by using slow motion maneuvering equation in the horizontal plane. The wind forces are calculated from emperical formula of ABS and the mooring forces of ropes and fenders are modeled as linear spring.

• 한국항해항만학회지
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• 제36권9호
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• pp.729-735
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• 2012

The primary wave energy conversion by a three-dimensional bottom-mounted oscillating water column (OWC) wave power device in regular waves has been studied. The linear potential boundary value problem has been solved following the boundary matching method. The optimum shape parameters such as the chamber length and the depth of the front skirt of the OWC chamber obtained through two-dimensional numerical tests in the frequency domain have been applied in the design of the present OWC chamber. Time-mean wave power converted by the OWC device and the time-mean second-order wave forces on the OWC chamber structure have been presented for different wave incidence angles in the frequency-domain. It has been shown that the peak period of $P_m$ for the optimum damping parameter coincides with the peak period of the time.mean wave drift force when ${\gamma}=0$.

• 한국기계연구소 소보
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• 통권14호
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• pp.135-144
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• 1985

A method is described to obtain the first order force and second order steady force on the fixed two dimensional submerged or semisubmerged cylinders at infinite depth of water due to regular waves. The first order diffraction wave velocity potential which describes the flow diffracted by a body is obtained numerically using source distribution method on the mean wetted surface. And a technique to remove the irregular frequency phenomena of the source distribution method is also applied. The second order steady force is calculates by means of direct integration of the pressures on the body as derived from the first order velocity potential and is also computed by means of reflection wave height derives from momentum conservation theory. The results are compared with those of published works, and show good agreement.

• 대한조선학회논문집
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• 제37권2호
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• pp.1-13
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• 2000

본 논문에서는 무한수심의 해양에서 파랑 중의 세장선에 작용하는 선형 및 비선형 동유체력의 계산을 위해 unified 이론을 적용하고자 한다. 세장선은 전진속도를 가지지 않는 것으로 가정하였으며, 이러한 가정은 FPSO, shuttle tanker 등과 같은 선박에 적용된다. Unified 이론을 적용하기 위해 우선 스트립 이론의 결과를 필요로 하며, 이를 위해 NIIRID를 이용하였다. 선형이론을 적용하여 선박의 동유력체 계수 및 운동응답특성들을 살펴보았으며, 이들 결과를 이용하여 2차 비선형 동유체력을 구하였다. Unified 이론은 2차원 결과를 단순히 합한 스트립 이론에 3차원 수정항을 더하기 때문에, 선형이론의 경우 heave 및 pitch 운동에 대해 3차원 panel 프로그램들과 비슷한 정확도를 기대할 수 있다. 특히 본 연구에서는 이러한 선형이론을 2차 동유체력의 계산으로 확장하였으며, 이러한 확장이 합리적인 결과를 주고 있음을 확인할 수 있었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.79-82
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• 2003

An aquaculture system for feeding the caged fishes in the open water is suggested for ocean application. Survival and operation conditions are defined at the conceptual design. Wave and current drag forces are discussed to determine the proper dimension of the aquaculture system and the related mooring system. Second order wave drift force at the survival condition is the dominant force, which be reduced by minimizing the superstructure open to the surface. Automation in feeding, sorting, cleaning is introduced to use the ongoing technology for quality product. The suggested system has advantage compared to onshore culturing, but not to shallow water culturing system. There is room for real application in future by the countries, such as Korea and Japan, which are in short of fish supply and have willingness to venture towards the ocean aquaculture.

• 한국해양공학회지
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• 제15권3호
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• pp.134-141
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• 2001

An experimental method to investigate the dynamic characteristics of buoys in extreme environmental condition is established. Because the buoy model requires a resonable size for accurate experiment, the test condition in model basin that satisfies the similarity law is hardly compatible with capability of test facilities. It is suggested that the linear wave component that is unable to satisfy similarity is separated with others. The model experiment is carried out with mitigated condition for the linear wave components while others including wave drift, current and wind are keeping the similarities. Then, the result can be extrapolated to give the dynamic behavior of buoys n extreme condition because linear wave component is solely responsibly to oscillatory buoy motion and other environmental components are applied as a initial tension. The similarity for current and wind conditions is viewed as equivalence of restoring forces. The validity of proposed method is examined with different types of standard ocean buoys and it indicates that the linearity of measured characteristics is assured with a limitation of resonable distance between test and estimated wave conditions.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.208-215
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• 2001

An experimental method to investigate the dynamic charasteristics of buoys in extreme environmental condition is established. Because the buoy model requires a resonable size for accurate experiment, the test condition in model basin that satisfies the similarity law is hardly met with capability of test facilities. It is suggested that the linear wave component that is unable to satisy similarity is separated with others. The model experiment can be carried out with mitigated condition for the linear wave components while others including wave drift, current and wind are keeping the similarities. Then the result is extrapolated to give the dynamic behavior of buoys in extreme condition because linear wave component is soley responsible to oscillatory buoy motion and other environmental components are applied as a initial tension. the similarity for current and wind conditions is viewed as equivalence of restoring forces. the validity of proposed method is examined with different types of standard ocean buoys and it indicates that the linearity of measured characteristics is assured with a limitation of resonable distance between test and estimated wave conditions.

• 한국해양공학회지
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• 제13권4호통권35호
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• pp.19-27
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• 1999

To design a very large floating structure, such as a floating airport, we have to estimate the hydroelastic responses of a very large floating structure (VLFS) exactly. We developed the numerical method for estimating the hydroelastic responses of the VLFS. The developed numerical approach is based on a combination of the three-dimensional source distribution method, the wave interaction theory and the finite element method for structurally treating the space frame elements. The Numerical results of the hydroelastic responses and steady drift forces of a somisubmersible type offshore structure, which is supported by the 33(3 by 11) floating bodies, with various bending rigidities are illustrated.

• 대한조선학회지
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• 제26권2호
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• pp.25-31
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• 1989

정규칙파 중에서의 이차원 주상체의 대진폭 운동이 시간영역 수치계산법에 의해 다루어졌다. 물체표면 경계조건을 각 순간의 실제 물체표면에서 적용하므로 대진폭 운동에서 고려되어야 하는 물체 위치변화 및 형상변화 등에 의한 비선형효과가 고려되고 있으며, 자유표면에서의 비선형효과는 고려되지 않는다. 단순강제동요 및 자유동요문제에 적용된 바 있는 물체 표면 소오스 분포와 자유표면 스펙트럴 표현방법이 입사파의 강제력을 포함하도록 확장 적용되었고 물체의 운동응답은 시간적분법에 의해 계산되었다. 잠수 및 부유주상체의 대진폭 운동이 시간영역에서 직접 시뮬레이션되어 비선형 효과들이 보여지고 있으며, 대진폭 운동시 파강제력에 영향을 미치는 비선형효과가 고찰되어, 물체와 유체입자의 상대운동이 수평 및 수직방향 시간평균력들에 상당한 영향을 미침이 보여지고 있다.

• Journal of Advanced Research in Ocean Engineering
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• 제3권2호
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• pp.83-101
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• 2017

In this study, the added resistances of the large container ship in head and oblique seas are evaluated using a time-domain Rankine panel method. The mean forces and moments are computed by the near-field method, namely, the integration of the second-order pressure directly on the ship surface. Furthermore, a weakly nonlinear approach in which the nonlinear restoring and Froude-Krylov forces on the exact wetted surface of a ship are included in order to examine the effects of amplitudes of waves on ship motions and added resistances. The computation results for various advance speeds and heading angles are validated by comparing with the experimental data, and the validation shows reasonable consistency. Nevertheless, there exist discrepancies between the numerical and experimental results, especially for a shorter wave length, a higher advance speed, and stern quartering seas. Therefore, the accuracies of the linear and weakly nonlinear methods in the evaluation of the mean drift forces and moments are also discussed considering the characteristics of the hull such as the small incline angle of the non-wall-sided stern and the fine geometry around the high-nose bulbous bow.