• International Journal of Naval Architecture and Ocean Engineering
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• 제2권1호
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• pp.14-23
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• 2010

A numerical model was developed for simulating a three-dimensional multilayer hydrodynamic and thermodynamic model in domains with irregular bottom topography. The model was designed for examining the interactions between flow and topography. The model was based on the three-dimensional Navier-Stokes equations and was solved using the fractional step method, which combines the finite difference method in the horizontal plane and the finite element method in the vertical plane. The numerical techniques were described and the model test and application were presented. For the model application to the northern part of Ariake Sea, the hydrodynamic and thermodynamic results were predicted. The numerically predicted amplitudes and phase angles were well consistent with the field observations.

• 한국물환경학회지
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• 제28권1호
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• pp.26-37
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• 2012

Multi-dimensional hydrodynamic and water quality models are widely used to simulate the physical and biogeochemical processes in the surface water systems such as reservoirs and estuaries. Most of the models have adopted the Eulerian grid modeling framework, mainly because it can reasonably simulate physical dynamics and chemical species concentrations throughout the entire model domain. Determining the optimum grid cell size is important when using the Eulerian grid-based three-dimensional water quality models because the characteristics of species are assumed uniform in each of the grid cells and chemical species are represented by concentration (mass per volume). The objective of this study was to examine the effect of grid-size of a three dimensional hydrodynamic and water quality model (EFDC) on hydrodynamics and mass transport in the Saemangeum Reservoir. Three grid resolutions, respectively representing coarse (CG), medium (MG), and fine (FG) grid cell sizes, were used for a sensitivity analysis. The simulation results of numerical tracer showed that the grid resolution affects on the flow path, mass transport, and mixing zone of upstream inflow, and results in a bias of temporal and spatial distribution of the tracer. With the CG, in particular, the model overestimates diffusion in the mixing zone, and fails to identify the gradient of concentrations between the inflow and the ambient water.

• 한국환경과학회지
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• 제11권1호
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• pp.25-32
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• 2002

In order to control of water quality in Jeju harbor, variation of physical oceanographic environments was estimated using material cycle model. It is composed of the three-dimensional hydrodynamic model for the simulation at water flow and material cycle model for the simulation of water quality. The three dimensional hydrodynamic model simulation of the circulation and mixing in Jeju Harbor has been conducted forced by Sanzi River Discharge, Tidal elevation, wind and Solar heat in case of August and November, 2000 and February and May, 2001, respectively. The results of numerical model and observation show that the model can produce realistic results of current in the harbor. The monthly variation of velocity pattern are not so much changed are found In Jeju Harbor. The residual current was forced by temperature, salinity, density, wind and tidal current. The residual current of August, 2000 are the strongest among four month. It can be explained that the density effect can be important role in residual current at Jeju Harbor. As the results of salinity distribution simulation, very low concentration of all levels were simulated in August, 2000. The flowrate of Sanzi river was investigated 77,760 ㎥ /d in August, 2000. Therefore, pollutant loadings from Sanzi river should be considered for water quality management in Jeiu harbor.

• 한국해안해양공학회지
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• 제12권1호
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• pp.1-10
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• 2000

해수유동 모델과 부영양화 모델로 구성된 3차원 생태계 모델을 수립하여 진해만에 적용하였으며, 해수유동 모델과 부영양화 모델은 동일한 격자상에서 운영된다. 수치계산결과를 관측경과와 비교하였으며, 그 결과 비교적 잘 일치하였다. 계산된 COD, DIN 및 DIP의 농도는 오폐수의 과다유입과 식물성 플랑크톤의 생산에 의해 진해만의 북부 지역(마산만)에서 높게 나타났다. 저층에서 저산소 및 무산소 수괴는 오폐수의 유입량이 많고 성층이 강하게 형성되는 진해만의 북부해역과 성층형성과 양식장이 밀집되어 있는 진해만의 서부 내만에서 발생하고 있다. DO 농도의 등분포선은 만 입구로부터 DO 공급과 물리적 작용에 의해 만 입구에서 만 내로 DO의 수송으로 인해 만의 입구와 평행하게 나타났다. 저층 저산소 수괴의 형성에 물리적, 생화학적 과정이 대단히 중요한 역할을 하며, 이 중에서 해수의 수평적·연직적 확산에 의한 물리적 작용이 제일 중요한 요소인 것으로 판단된다.

• 한국해양공학회지
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• 제32권6호
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• pp.474-484
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• 2018

In this study, a new numerical modeling system was proposed to predict oil spills, which increasingly occur at sea as a result of abnormal weather conditions such as global warming. The hydrodynamic conditions such as the flow velocity needed to calculate oil dispersion were estimated using a three dimensional hydrodynamic model based on the Navier-Stokes equation, which considered all of the physical variations in the vertical direction. This improved the accuracy compared to those estimated by the conventional shallow water equation. The advection-diffusion model for the spilled oil was combined with the hydrodynamic model to predict the movement and fate of the oil. The effects of absorption, weathering, and wind were also considered in the calculation process. The combined model developed in this study was then applied to various test cases to identify the characteristics of oil dispersion over time. It is expected that the developed model will help to establish initial response and disaster prevention plans in the event of a nearshore oil spill.

• 한국물환경학회지
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• 제27권4호
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• pp.413-424
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• 2011

The study was aimed to evaluate the applicability of a three-dimensional (3D) hydrodynamic and water quality model, ELCOM-CAEDYM for Yongdam Reservoir, Korea. The model was applied for the simulations of hydrodynamics, thermal stratification processes, stream density flow propagation, and water quality parameters including dissolved oxygen, nutrients, organic materials, and algal biomass (chl-a) for the period of June to December, 2006. The field data observed at four monitoring stations (ST1~ST4) within the reservoir were used to validate the models performance. The model showed reasonable performance nevertheless low frequency boundary forcing data were provided, and well replicated the physical, chemical, and biological processes of the system. Simulated spatial and temporal variations of water temperature, nutrients, and chl-a concentrations were moderately consistent with the field observations. In particular, the model rationally reproduced the succession of different algal species; i.e., diatom dominant during spring and early summer, after then cyanobacteria dominant under warm and stratified conditions. ELCOM-CAEDYM is recommendable as a suitable coupled 3D hydrodynamic and water quality model that can be effectively used for the advanced water quality management of large stratified reservoirs in Korea.

• 한국환경과학회지
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• 제15권10호
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• pp.951-960
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• 2006

The eco-hydrodynamic model was used to estimate the environmental capacity in Gamak Bay. It is composed of the three-dimensional hydrodynamic model for the simulation of water flow and ecosystem model for the simulation of phytoplankton. As the results of three-dimensional hydrodynamic simulation, the computed tidal currents are toward the inner part of bay through Yeosu Harbor and the southern mouth of the bay during the flood tide, and being in the opposite direction during the ebb tide. The computed residual currents were dominated southward flow at Yeosu Harbor and sea flow at mouth of bay, The comparison between the simulated and observed tidal ellipses at three station showed fairly good agreement. The distributions of COD in the Gamak bay were simulated and reproduced by an ecosystem model. The simulated results of COD were fairly good coincided with the observed values within relative error of 1.93%, correlation coefficient(r) of 0.88. In order to estimate the environmental capacity in Gamak bay, the simulations were performed by controlling quantitatively the pollution loads with an ecosystem model. In case the pollution loads including streams become 10 times as high as the present loads, the results showed the concentration of COD to be $1.33{\sim}4.74mg/{\ell}(mean\;2.28mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality In case the pollution loads including streams become 30 times as high as the present loads, the results showed the concentration of COD to be $1.38{\sim}7.87mg/{\ell}(mean\;2.97mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality. In case the pollution loads including streams become 50 times as high as the present loads, the results showed the concentration of COD to be $1.44{\sim}9.80mg/{\ell}(mean\;3.56mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality.

• 한국해양환경ㆍ에너지학회지
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• 제14권2호
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• pp.121-129
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• 2011

EFDC 모형에서 해수유동과 퇴적물 이동을 모의하고자 하는 경우에 필요한 해수유동과 퇴적물 이동 모듈외의 수질 모델 등의 요소가 해수유동 모의시간에 미치는 영향을 검토하였다. 해수유동과 퇴적물 이동의 계산에 불필요한 수질요소관련 프로그램과 조건문 들을 모델에서 제거하는 방법으로 모형을 간략화하고 계산시간을 비교하였다. 수정된 EFDC 모형(EFDC-E)을 사용하여 목포해역에서 조류에 대하여 모의하고, 계산에 소요되는 시간과 모의결과를 EFDC 모형을 이용한 모의결과와 비교하였다. 또한, 2차원 모형과 3차원 모형을 동시에 적용하여 2차원 모의결과와 3차원 모의결과의 차이점에 대한 분석과 각 모형의 목포해역 조류 비대칭에 대한 재현성에 대해서 검토하였다. 간략화과정을 통해서 개선된 EFDC-E 모형은 EFDC 모형보다 2차원과 3차원 조류모의에서 약 3배 빠르게 계산하는 것을 확인할 수 있었다. 2차원 모의결과는 수심평균유속을 계산하여 상층에서 관측한 조류를 정확하게 재현하지 못하였으나, 3차원 모형을 적용한 결과는 2차원 모의보다 유속크기가 관측치와 보다 잘 일치하는 모습을 보였다.

• 한국수자원학회논문집
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• 제38권11호
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• pp.973-984
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• 2005

3차원 열동수역학 모형을 개발하여 지형학적으로 복잡한 자연 저수지에서 안정한 성층류의 선택 취수를 부정류 모의하였다. 지배방정식은 2차 정확도의 유한체적법을 이용하여 해석하였다. 개발된 수치모형을 3차원 난류, 성층화된 전단층흐름에 적용하여 검정을 하였다. 수치해석결과는 실험실에서 관측된 선택취수시의 속도 및 온도분포의 일반적인 형상을 양호하게 예측하는 것으로 나타났으나, 자연 저수지에서의 흐름에 대한 적용시에는 속도의 크기를 과대모의 하는 것으로 나타났다. 수치모의에서 구해진 선택취수의 물리적 특성을 논하였다.

• 한국해양공학회지
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• 제8권2호
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• pp.124-130
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• 1994

This paper compared with the hydrodynamic interference acting on the semi-submersible element model with 1-lowerhull and 2-columns. In this case, calculation are applying the strip method and 3-dimensional source distribution method. As the wave frequency and the distance between increase, the influence effects of parts upon each other decrease and approach the results calculated by using the strip method. Thus, it can be prepared for the investigation of new practical method of investigation of new practical method of hydrodynamic forces acting on huge structures.