• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.29-33
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• 2002

A procedure of free span and fatigue analysis of offshore pipelines was made per DNV-RP-F105, 2002. The new method includes the axial force and deflection load in pipelines. The screening criteria were used to calculate the allowable span lengths. The screening criteria allow small amplitudes of vortex-induced vibration due to wave and current loading. However, the induced pipe stress is very small and usually below the limit stress of a typical S-N curve. A simplified method was established to calculate the fatigue damage due to long-term current distribution. The long-term current statistics was assumed with a 3-parameter Weibull distribution. The fatigue damage was estimated for the span lengths obtained from the screening criteria for various conditions. Sample calculations show the effect of axial force for various boundary conditions.

• 한국해양공학회지
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• 제21권6호
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• pp.87-94
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• 2007

This study used POM (Princeton ocean model) improved for applying to coastal area in order to predict the distribution of thermal waste water. This model was applied to the coastal circulation and the effect of thermal waste water of Cheonsu-Bay. So this study compared the discharge of thermal waste water with each layer and section. The tidal current was about 1.5 m/sec at surface level and 0.9 m/sec on bottom level at flood tide; tidal current was about 1.3 m/sec on surface level and 0.8 m/sec on bottom level at ebb tide. The method discharging the thermal waste water in the nearshore region (case 1) accelerates the diffusion of the thermal waste water in the north-south direction(longshore direction). However, the method discharge the thermal waster water in the offshore region (case 2) reduced the diffusion of the thermal waste water over the coastal region. According th the diffusion region of the thermal waste water with case 1 and case 2 at three different layers (surface, middle, bottom), the diffusion region by case 1 discharge method generally influenced wider region (twice) than the one by case 2 discharge method with lower temperature between $1^{\circ}C\;and\;2^{\circ}C$, whereas the case 2 discharge method influenced the deeper region (middle and botton layers) with higher change of the water temperature ($1{\sim}3^{\circ}C$).

• Computers and Concrete
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• 제13권1호
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• pp.117-133
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• 2014

This study presents a rapid method for determining the steady state migration coefficient of concrete by measuring the electric current. This study determines the steady state chloride migration coefficient using the accelerated chloride migration test (ACMT). There are two stages to obtain the chloride migration coefficient. The first stage, the steady-state condition was obtained from the initial electric current at the beginning of ACMT. The second stage, the average electrical current in the steady state condition was used to determine the steady state chloride migration coefficient. The chloride migration coefficient can be determined from the average steady state current to avoid sampling and analyzing chlorides during the ACMT.

• 한국해양공학회지
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• 제11권4호
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• pp.141-151
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• 1997

This paper deals with a numerical study of flow-guider applied to controlling current in a bay. Two dimensional numerical model for tidal currents based on the depth averaged equation is developed and standard k-.epsilon. model is adopted to determine the turbulence diffusion. Equations are described in a generalized coordinate system to be implemented by non-staggered grid system and discretized by using finite volume method. Unsteady flow is simulated by fully implicit scheme. Hybrid scheme and central differencing are used to compute the convective terms and source terms, respectively. The tidal current in a rectangular bay is simulated and it gives satisfactory results. The realistic and distinct models of a large structure placed in bay are also exemplified with or without flow-guiders. The simulation results show that the flow-guider gives the residual tidal current in the bay by the different flux with respect to the direction of tidal current.

• 한국해안해양공학회지
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• 제5권2호
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• pp.76-83
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• 1993

Miche의 쇄파기준을 활용하여 쇄파 발생시에도 적용할 수 있는 파낭모형을 제시하였고 이 모형을 근간으로 하여 천해역에서의 방향성 파낭 Spectrum에 쇄파로 인한 에너지 소산을 도입할 수 있는 기법을 개발하였다. 본 연구에서 제안된 기법의 타당성을 검증하기 위하여 천해성에서 shear current, upwelling current와 조우하는 방향성 Wallops 파랑 spectrum에 적용하였다.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2018년도 공동국제학술발표회
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• pp.149-149
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• 2018

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1995년도 정기학술강연회 발표논문 초록집
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• pp.20-25
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• 1995

Surface wind field over an ocean plays a very important role not only to generate wind-driven current, but also to control heat exchange between ocean and atmosphere. However, the surface wind-field used for the ocean circulation and heat exchange is usually estimated by indirect methods because of lack of observed wind data and incomplete spatial coverage. (omitted)

• Journal of the korean society of oceanography
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• 제32권1호
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• pp.1-7
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• 1997

Surface current fields in the eastern East China Sea (ECS) were constructed by analyzing trajectories of 58 satellite-tracked surface drifters released during 1991-1996. Composite trajectories and 20-minute-by-20-minute box-averaged current vectors show that the basic current pattern composes of: the Kuroshio main stream, which turns eastward toward the Tokara Strait; a northward branch current of the Kuroshio on the ECS outer shelf deeper than 100 m; and an anticyclonic circulation in the northern Okinawa Trough west of Kyushu. The northward branch current sharply changes its direction to the northeast when it crosses a line connecting Cheju Island, Korea and Goto Islands, Japan. The basic pattern of current field changes slightly from winter to summer, and the main axis of the Tsushima Current in the Korea Strait is found to shift seasonally. The drifter experiment does not support the claim that the Yellow Sea Warm Current is separated from the northward branch current on the outer shelf southeast of Cheju Island. We suggest that the use of the term 'Tsushima Current' be limited to the northeast channel flow in the Korea Strait. The new term 'Kuroshio Branch Current' is suggested for the northward branch current on the outer shelf south of Cheju-do, which is separated from the Kuroshio.

• 한국해안·해양공학회논문집
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• 제25권4호
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• pp.207-218
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• 2013

수치 모델링 실험을 활용하여 서해 천수만의 해수 유동과 그 변화를 이해하기 위한 연구를 수행했다. 모델링 실험 결과에 대한 검증을 위해 관측 자료의 조위와 조류 각각 4대 분조의 진폭과 위상을 이용하여 스킬 분석을 실시했다. 그 결과 스킬 점수는 대부분 90%가 넘는 것으로 보아 수치 모델링 실험 결과는 관측된 조위와 조류가 양호하게 일치하는 것으로 나타났다. 천수만의 조석파는 만 입구에서 안쪽으로 진행되며 북부로 갈수록 조차는 점차 증가했다. 조석파가 북부까지 도달하는데 약 10~30분의 시간이 소요되었다. 남부에서 조석파는 반시계 방향으로 회전하는 특성을 보였다. 조류는 해저 지형을 따라 남-북 방향으로 흘렀으며, 장축의 각도는 등수심선과 나란히 나타났다. 조류타원의 단축이 장축의 10% 이하로 왕복성 조류의 특성을 보였다. 수심과 해안선 등 지형적 요인에 의해 좌우되는 조석잔차류의 크기는 1~30 cm/sec의 범위를 보였고, 남쪽 수로에서 컸으며 만의 북부에서는 작았다. 조석잔차류로부터 유도된 상대와도를 통해 수 백 m에서 수 km 크기로 시계/반시계 방향으로 회전하는 와류를 확인했고, 죽도 주변에서 2쌍, 남부에서 형성된 3~4쌍의 강한 와류 특성을 파악했다.

• 한국해양공학회지
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• 제31권1호
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• pp.36-46
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• 2017

Most of the studies on the hydraulic characteristics of wave-current interaction have used 2-D hydraulic experiments or 2-D numerical simulations. However, it is difficult to understand the wave-current interaction found in actual estuaries using these. Therefore, a numerical water tank was constructed in this study to perform simulations involving a 3-D river mouth. The result showed a change in the water surface at the river mouth from the wave-current interaction. With an increase in the ratio ($V_c/C_i$) between the river current and wave celerity, the wave height and mean water level of the river increased at the wave and current meeting point. A higher $V_c/C_i$ caused a stronger wave-current interaction and increased the turbulence kinetic energy. Thus, the wave height attenuation became larger by the wave-current interaction with a higher $V_c/C_i$. In addition, it was possible to understand the flow characteristics in the vicinity of the river mouth as a result of the wave-current interaction using the mean flow and mean time-averaged velocity at the mid-cross section of river.