• 한국시뮬레이션학회논문지
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• 제20권1호
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• pp.97-105
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• 2011

하천에서, 생물막은 녹갈색의 얇은 막의 형태로 돌, 식물, 그리고 기타 구조물의 표면에 부착되어 있다. 생물막은 주로 영양물의 순환, 수질정화, 바닥 침전물 제거, 그리고 먹이사슬내의 에너지 흐름에 매우 중요한 역할을 한다. 본 연구에서, 우리는 유체 흐름 안에서, 독소-생산 종과 독소-민감 종의 복합적 생물막을 전산 모사하는 모델을 개발하였다. 유체 흐름으로는 균일한 흐름과 불 균일한 흐름 두 가지를 고려하였다. 균일한 흐름은 확률 프로세스로 구현되었으며, 불 균일한 흐름은 나비어-스톡스 방정식으로 구현되었다. 모델에서, 독소-생산종과 독소-민감종 간의 상호작용을 고려하기 위해, 종 개체의 번식률과 사망률이 고려되어졌다. 우리는 서로 다른 두 유체 흐름 내에서 전산 모사 되어진 생물막의 구조적 형상에 대해서 간략히 논의 하였다.

• 한국해안해양공학회지
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• 제4권2호
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• pp.91-107
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• 1992

Heaps(1972)가 사용한 천해균질류에 대한 선형 기본방정식을 수심평균류속과 해수면변리를 계산하는 External mode와 수심변이 유속을 계산하는 Internal mode로 분리시킨 다음, Internal mode식에 Galerkin Method를 적용하였다. Internal mode유속을 수평좌표, 시간에 따라 변하는 계수와 대직좌표에 따라 변하는 Basis function들의 곱의 형태로 선형전개하며, 난류확산계수를 포함하는 2차미분항으로부터 해수면에 Homogeneous boundary condition과 해저면에 Sheared boundary condition이 가해지는 Sturm-Liouville system을 구성, Eigenfunctions 해를 구하여 Basis function으로 사용하였다. 모델의 성능을 검토하기 위하여 수립된 모델을 정상균일풍이 가해지는 1차원 수노에 적용하여 Cooper and Pearce(1977)가 제시한 해저면 비활동조건하의 무한 및 유한수노 연직류원분포에 대한 해석각와 비교하였으며, North Sea 규모의 등수심 장방형 Basin(Heaps' Basin)에 적용하여 정상균일풍에 대한 Heaps(1972)의 계산결과와 비교하였다.

• 한국항해항만학회지
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• 제35권3호
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• pp.197-204
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• 2011

회류수조에서의 대각도 정적(static) 모형실험을 통해 Manta형 무인잠수체에 작용하는 동유체력을 측정하였으며, 동유체력에 미치는 Reynolds수의 영향을 고찰하였다. 이를 위해 동유체력을 cross-flow drag과 양력(lift force)으로 성분 분석을 하였으며, 양력 성분에는 Reynolds수의 영향을 무시하고, cross-flow drag 성분에만 Reynolds수의 영향을 고려하였다. 그 후 이들 두 성분을 다시 합성함으로써 실물 무인잠수정에 작용하는 동유체력의 추정 기법을 제시하였다.

• 물과 미래
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• 제24권4호
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• pp.41-48
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• 1991

본 연구는 2차원비선형 동수역학방정식을 이용하여 가막만의 조류의 특성을 해석하였다. 사용된 기초방정식은 Navier-Stokes의 운동 및 연속방정식이 이용되었고, 방정식을 구성하는 각항의 특성에 관해 상세하게 살펴본 후, 그것을 음적차분법을 사용하여 수치해석하였다. 수치모델은 2차원 단층모델로 구성하였으며, 수립된 수치모델을 가막만에 적용하여, 해의 안정성과 수렴성을 검토하였으며, 모델의 결과와 현지의 관측치를 비교하여 수치모델의 재현성을 검토하였다. 본 수치실험결과 다음의 것들이 증명되었다. I) 실측치와 비교해서 조류의 유향, 유속에 대해서 재현성은 양호하게 나타났으며, II) 안정해를 얻기위한 조석주기는 4주기었다. 또한, III) 조도계수는 C=(1/n)$h^{1/6}$으로 충분히 나타낼수 있었다.

• 대한기계학회논문집B
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• 제31권7호
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• pp.620-627
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• 2007

In this paper, we adapt a modified internal energy non-equilibrium first-order extrapolation thermal boundary condition to the thermal lattice Boltzmann model (TLBM). This model is the double populations approach to simulate hydrodynamic and thermal fields. The bounce-back boundary condition which is a traditional boundary condition of lattice Boltzmann method has only a first order in numerical accuracy at the boundary and numerical instability. A non-equilibrium first-order extrapolation boundary condition has been verified to be of better numerical stability than the bounce-back boundary condition and this boundary condition is proved to be of second-order accuracy for the flat boundaries. The two-dimensional natural convection flow in a square cavity with Pr=0.71 and various Rayleigh numbers are simulated. The results are found to be in good agreement with those of previous studies.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회 논문집
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• pp.1184-1188
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• 2005

The impacts of turbidity flow induced by summer rainfall events on water supply, aquatic ecosystems, and socioeconomics are significant and major concerns in most of reservoirs operations. As a decision support tool, the real-time turbidity flow monitoring and modeling system RTMMS is under development using a laterally integrated two-dimensional (2D) hydrodynamic and water quality model. The objectives of this paper is to present the preliminary field observation results on the characteristics of rainfall-induced turbidity flows and their density flow regimes, and the model performance in replicating the fate and transport of turbidity plume in a reservoir. The rainfall-induced turbidity flows caused significant drop of river water temperature by 5 to $10^{\circ}C$ and resulted in density differences of 1.2 to $2.6kg/m^3$ between inflow water and ambient reservoir water, which consequently led development of density flows such as plunge flow and interflow in the reservoir. The 2D model was set up for the reservoir. and applied to simulate the temperature stratification, density flow regimes, and temporal and spatial turbidity distributions during flood season of 2004 After intensive refinements on grid resolutions , the model showed efficient and satisfactory performance in simulating the observed reservoir thermal stratification and turbidity profiles that all are essentially required to enhance the performance of RTMMS.

• Journal of Advanced Research in Ocean Engineering
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• 제1권1호
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• pp.14-24
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• 2015

A three-dimensional multidirectional nonlinear numerical wave tank (NWT) based on the Navier-Stokes equations and the Finite Volume Method (FVM) is developed by using the two-phase hydrodynamic flow solver naoe-FOAM-SJTU based on the open source toolbox OpenFOAM. The free surface is capturing with the Volume Of Fluids (VOF). The directional wave including Stokes wave, solitary wave and nonlinear wave are simulated and verified. The multi-directional waves are also simulated with particular wave spectral such as JONSWAP and wave directional spreading function. The obtained numerical results show the capability of the solver to generate different type of multidirectional nonlinear waves accurately. Meanwhile, it implies that the presented NWT can easily extend to model the wave-structures interactions, which will be great help to the offshore structures design.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.305-310
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• 2005

The velocity and pressure fields of a ship's propulsion mechanism of the Weis-Fogh type, in which a airfoil moves reciprocally in a channel, are studied in this paper using the advanced vortex method. The airfoil and the channel are approximated by a finite number of source and vortex panels, and the free vortices are introduced from the body surfaces. The viscous diffusion of fluid is represented using the core-spreading model to the discrete vortices. The velocity is calculated on the basis of the generalized Biot-Savart low and the pressure field is calculated from integrating the equation given by the instantaneous velocity and vorticity fields. Two-dimensional unsteady viscose flows of this propulsion mechanism are numerically clarified, and the calculated results agree well with the experimental ones.

• 한국환경과학회지
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• 제16권4호
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• pp.495-503
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• 2007

In this study, we took the geometrical character of the river channel junction and hydrologic conditions as independent variables, and hydraulic behavior characteristics as an independent variable. The result, after multiple analysis was carried out, proved that, except for the generating area of the accelerating zone of velocity the accelerating zone and both the main channel and the tributary zone of stagnation the stagnation zone, there was correlation of over 90%. Also, derived presumed expression of the hydraulic characteristics of the junction was applied to the real natural channel - the river channel of the Guem-ho main channel(the A-yang bridge to the Guem-ho bridge). As the result, it proved that it represented hydraulic characteristics relatively well.

• International Journal of Ocean System Engineering
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• 제4권1호
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• pp.49-56
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• 2014

A three-dimensional multidirectional nonlinear numerical wave tank (NWT) based on the Navier-Stokes equations and the Finite Volume Method (FVM) is developed by using the two-phase hydrodynamic flow solver naoe-FOAM-SJTU based on the open source toolbox OpenFOAM. The free surface is capturing with the Volume Of Fluids (VOF). The directional wave including Stokes wave, solitary wave and nonlinear wave are simulated and verified. The multi-directional waves are also simulated with particular wave spectral such as JONSWAP and wave directional spreading function. The obtained numerical results show the capability of the solver to generate different type of multidirectional nonlinear waves accurately. Meanwhile, it implies that the presented NWT can easily extend to model the wave-structures interactions, which will be great help to the offshore structures design.