• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.123-135
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• 1995

A numerical procedure is described for predicting steady drift forces an multiple three-dimensional bodies of arbitrary shape freely floating in waves. The developed numerical approach is based on combination of a three-dimensional source distribution method, wave interaction theory art the far-field method using momentum theory. Numerical results are compared with the experimental or numerical ones, which are obtained in the literature, of steady drift forces on 33(3 by 11) floating composite vertical cylinders in waves. The results of comparison confirmed the validity of the proposed approach. Finally, the interaction effects are examined in the case of an array of 40(4 by 10) freely floating rectangular bodies in shallow water.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.173-174
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• 2023

IAMSAR Manual 국문본인 국제항공 및 해상수색 구조편람에 따른 확대사각(SS: Expanding Square Search) 수색패턴은 수색 대상의 표류 위치를 한정할 수 있을 때 적용하도록 하고 있으며, 수색 기법에 있어 추측항법 적용의 필요성과 함께 조난대상의 표류 추정 위치인 Datum으로부터의 첫 번째 수색 방향 S의 결정은 바람이 불어오는 쪽인 풍상 측을 향하도록 하여 항해 오차를 최소화할 것을 요구하고 있다. 그러나 첫 직행 구간 S 결정에 있어 IAMSAR Manual 영문본 및 USCG SAR Manual에 따르면 S는 풍하 측 또는 표류하는 방향으로 결정하는 것이 옳은 것으로 해석될 수 있으며 이는 항해 오차를 최소화하기 위한 추측항법 적용 관점에도 부합하는 것으로 보이는바, 이 연구에서는 USCG SAR Manual 등 다른 수색 지침서에서는 Drift 방향으로 제시한 첫 번째 S 방향을 근거로 IAMSAR Manual 국문본의 오류 가능성을 제시하였고, 풍상과 풍하 측으로 상반된 첫 번째 S 방향에 따른 수색 결과의 비교를 위해 선박조종시뮬레이션을 활용, 확대사각 수색상황을 재연하여 각각의 수색패턴을 비교 분석하였다. 이를 통하여 확대사각 수색패턴 결과에서 수색 대상에 더욱 근접한 첫 번째 S 방향은 수색 대상이 표류하는 방향과 일치하는 풍하 측임을 확인하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.2
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• pp.92-99
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• 1991

A moored body in the sea is subjected to second-order wave forces as well as to linear oscillatory ones. The second-order farces contain slowly-varying components, of which the characteristic frequency can be as low as the natural frequency of horizontal motions of the moored body. As a consequence, the slowly-varying force can excite unexpectedly large horizontal excursion of the body, which may cause a serious damage on the mooring system. In design analysis of Turret-type mooring system which is one of the interesting mooring systems for a floating body. the slowly-varying drift forces and the transient motion of the system during weathervaning are very important. In this paper the slowly-varying drift forces were calculated by using the Quadratic Transfer Function with considering the second order free-wave contributions. Additionaly the transient surge motion of the moored body was simulated with including the roll of the time-memory effect. In this simulation the spring constant of the spread Turret mooring system is updated at every time step for considering the nonlinear effect.

• Journal of Navigation and Port Research
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• v.26 no.2
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• pp.221-226
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• 2002

To provide reliable data for drift prediction models, field experiments were carried out in the coastal region off Busan port. Four different size of vessels(10, 30, 50, 90G/T ton) were deployed for the experiment. Among them G/T 50ton class vessel was equipped with instruments measuring the currents, winds, headings and trajectory data. In the rest of vessels only the position data were recorded for the purpose of target divergence study. The trajectories of each vessel were measured by DGPS(Differential Global Positioning System) and collected by APRS(Automatic Position Reporting System). The experiment was done in wind of 2~10m/s and current of 0.5~1.5m/s. The leeway was derived by subtracting surface current velocity from target drifting velocity. The leeway rate of G/T 50ton vessel was found to be about 3.6% and the computed leeway speed equation was $U_L$=0.042 W - 0.034. The processed leeway angle data were deflected by $-30^{\circ}$~$40^{\circ}$ from the direction of ship drift.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.4
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• pp.379-392
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• 1995

An initial attempt to establish predictive system of sea surface current and trajectories of drifting bodies for seas adjacent to Korea is described. A predictive system for the Korea Strait area was first set up based on Data Tables for surface tidal currents, surface wind-driven currents and density-driven currents. Simulations thus performed were in general agreements with satellite tracking buoy observations available in this region.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.7-12
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• 2000

As the offshore oil fields are moved to the deep ocean, the oil production systems of FPSO(Floating production storage and offloading system) are building these days and so it is the most important to estimate the drift motion and damping effects the drift motion importantly. The components of damping consist of viscous, wave radiation effect and wave drift damping. It is need to estimate the wave drift damping exactly among them. The wave drift damping means the change rate of mean wave drift force with respect to the ship and ocean structures speed. In order to calculate this, the 3-Dimensional panel method used to translating and pulsating Green function is adopted. The calculation is carried out for series 60(CB = 0.7) vessel and the results are compared with other theoretical ones.

• The Korean Journal of Financial Studies
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• v.10 no.1
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• pp.1-44
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• 2004

연속시간모형은 시간의 흐름에 대응되는 자본자산의 운동의 성질과 시간의 흐름에 따라 형성되는 자본자산의 가격을 동시적으로 파악할 수 있는 것이 큰 장점이다. 연속시간 확률미분방정식을 구성하는 표류함수와 확산함수가 폐형해나 해석적 형태로 존재하지 않는 경우가 대부분이다. 여기에서 모수추정의 어려움이 발생한다. 전이 확률밀도함수의 인지 또는 발견의 어려움과 표류함수와 확산함수의 적분 불가능성은 최대가능도법의 사용을 어렵게 만든다. 여기에서 모수방법 보다는 비모수방법을 통하여 연속 확률 미분방정식을 추정하려는 성향이 존재한다. 밀도를 모르면 표본적률을 사용하여 모수를 추정할 수 있으므로 일반화 적률법이 연속시간 확률미분방정식의 모수 추정과 검정에 사용되고 있다. 전이밀도의 값을 시뮬레이션을 통하여 얻는 마코브연쇄 몬테카를로 방법, 전이밀도를 무한소 생성작용소를 통하여 얻는 방법, 비 모수방법, 여러 종류의 전개에 의하여 얻은 표류함수와 확산함수의 전이밀도에 대한 최대가능도법 등 여러 종류의 연속시간 확률미분방정식의 실증분석에서 사용되고 있다. 이 논문에서는 연속시간 확률미분방정식의 실증분석 방법들을 정리하는데 목적이 있다. 이일균(2004)은 이 논문과의 자매논문으로 시뮬레이션에 의한 확률미분방정식의 추정을 다루고 있어 시뮬레이션방법은 그 논문에 미룬다.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.222-227
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• 2001

The time simulation of slow drift motions of moored FPSO in waves is presented. The equation of motion based on Cummin's theory of impulse responses are employed, and are consisted of horizonal plane -surge, sway and yaw. The added mass coefficients, wave damping coefficients, first order wave exciting forces and the second order wave drift forces involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The mooring lines are modeled quasistatically as catenary for chains and touchdown. As for numerical example, time domain analyses are carried out for a box-type FPSO in long crest irregular wave condition.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.17-22
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• 2000

As the offshore oil fields are moved to the deep ocean, the oil production system of FPSO(Floating Production Storage and Offloading System) Type are constructed frequently these days. So, it is very important to estimate the drift motion and damping effects due to the drift motion simultaneously. The components of slow drift motion damping consist of viscous, wave radiation effect and wave drift damping. It is needed to estimate the wave drift damping more accurately than others. The wave drift damping signifies the time-rate of mean wave drift force on oscillating ship or ocean structure which constant speed. In order to calculate this, the 3-Dimensional panel method is employed with the translating and pulsating Green function in the frequency domain. The calculation is carried out for a Series 60 ($C_B$/=0.7) and the results are compared with other numerical ones.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.4
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• pp.350-361
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• 1995

For the Purpose of the measurement of drifting condition of the anchovy drift gill net, some experiments were carried out in M. S Seong-Yang at the near sea of Kampo harbor in Korean east sea from August to October 1994, by using three set of GPS equipped with her net. The main results obtained are as follows : 1) In fixed position by GPS at Taebyon, the radius of 95% probability and shifted distance from standard position were respectively 79.8m, 21.0m. 2) The mean values of PDOP and HDOP of GPS at Taebyon were respectively 3.5, 1.9 and the stability of the position by GPS at Taebyon was found to be very high. 3) In the fishing ground of the position from Lat. $35^{\circ}$ 41.5'N to $Lat^{\circ}$. 43.5', from Long. $129^{\circ}$ 32.0'E to Long. $129^{\circ}$ 32.5'E, the direction of the whole stretched drift gill net was $190^{\circ}$ and the direction of the whole casted net was $200^{\circ}$ when casting the net was finished. When whole net was found to be drifting into the direction of $170^{\circ}\;to\;180^{\circ}$, and the mean drifting speed of that was 0.82kt. 4) In the fishing ground of the position from Lat. $35^{\circ}$ 44.0'N to Lat. $35^{\circ}$ 45.2'N, from Long. $129^{\circ}$ 30.1'E to Long. $129^{\circ}$ 31.2'E, the direction of the whole stretched net was 20$^{\circ}$ and the direction of the whole stretched net was $20^{\circ}$ when casting the net was finished. When hauling the net, the direction of the spreaded net appeared from the North into the South and the whole net was found to be drifting into the direction of $210^{\circ}\;to\;220^{\circ}$, and the mean drifting speed of that was 0.75kt. 5) In the fishing ground of the positioning from Lat. $35^{\circ}$ 44.9'N to Lat. $35^{\circ}$ 46.0'N, Long. $129^{\circ}$ 33.0'E to Long. $129^{\circ}$ 34.0'E, the direction to the whole stretched net was $35^{\circ}$ and the direction of the whole casted net was $50^{\circ}$ when casting the net was finished. When hauling the net, the direction of the spreaded net appeared into the South from the East and the whole net was found to be drifting into the direction of $330^{\circ}\;to\;40^{\circ}$, and the mean drifting speed of the was 0.63kt.