• 한국환경과학회지
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• 제11권7호
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• pp.679-686
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• 2002

Turbulence greatly influence on atmospheric flow field. In the atmosphere, turbulence is represented as turbulent diffusion coefficients. To estimate turbulent diffusion coefficients in previous studies, it has been used constants or 2-level method which divides surface layer and Ekman layer. In this study, it was introduced Smagorinsky method which estimates turbulent diffusion coefficient not to divide the layer but to continue in vertical direction. We simulated 3-D flow model and TKE equation applied turbulent diffusion coefficients using two methods, respectively. Then we showed the values of TKE and the condition of each term to TKE. The results of Smagorinsky method were reasonable. But the results of 2-level method were not reasonable. Therefor, it had better use Smagorinsky method to estimate turbulent diffusion coefficients. We are expected that if it is developed better TKE equation and model with study of computational method in several turbulent diffusion coefficients for reasonably turbulent diffusion, we will able to predict precise wind field and movements of air pollutants.

• 대한기계학회논문집B
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• 제27권4호
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• pp.415-423
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• 2003

The hydrodynamic instability of the three-dimensional boundary-layer over a rotating disk has been numerically investigated for these flows; Ro = -1, -0.5, and 0, using linear stability theory. Detailed numerical values of the disturbance wave number. wave frequency. azimuth angle. radius (Reynolds number, Re) and other characteristics have been calculated for the pre-swirl flows. On the basis of Ekman and Karman boundary layer theory, the instability of the pre-swirl flows have been investigated for the unstable criteria. The disturbance will be relatively fast amplified at small fe and within wide bands of wave number compared with previously known Karman boundary-layer results. The flow (Ro =-0.5) is found to be always stable for a disturbance whose dimensionless wave number is greater than 0.9. It has a larger range of unstable interval than Karman boundary layer and can be unstable at smaller Re.

• 한국해양환경ㆍ에너지학회지
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• 제4권2호
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• pp.35-42
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• 2001

한국 남동해역 취송순환에서의 부정확한 외력의 바람응력 문제에 대한 최적화 방법의 유용성에 관하여 검토하였다. 바람응력은 모델 및 수치적 정식화 과정에서 상층 경계조건 및 외력항으로 고려되었다. 그리고 바람응력 평가에 대한 최적화 방법의 적용성 및 모델변수의 초기값 추정치의 중요성을 검토하였다. 최적화 연구로부터 동해 남부해역의 취송순환에 관한 동한난류의 수송량 변화 및 통해 난수층의 형성과 분포특성을 바람응력, 바람응력 회전성 및 상층두께의 변동으로부터 파악할 수 있음을 확인하였다.

• 한국수산과학회지
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• 제22권6호
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• pp.415-423
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• 1990

In a laboratory model the response of the boundary layer flow over topography is studied in a rotating sliced cylinder by employing the source-sink analogy with Ekman layer dynamics. The boundary layer flow is produced by two different fluid. In the first experiment homogeneous fluid is used both for the source and the working fluid of the container. In the second experiment a denser fluid is used for the source with the same working fluid. For the homogeneous western boundary layer flow both the northward and the southward flow were affected by the topography(ridge) to produce a cyclonic motion near the ridge. When woughward moving heavy boundary flow of slower speed and the northward moving faster flow were present at the same time, the splitting of southward flow and the separating of the northward flow were observed with a cyclonic motion at the ridge. The most important factor that influence production of the cyclonic motion has been turned out to be the presence of the topography in the western boundary layer. In particular the role of the southward moving heavy flow over the interior flow pattern was found to be very significant.

• 한국가시화정보학회지
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• 제9권1호
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• pp.49-54
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• 2011

An investigation has been made of a viscous incompressible flow in a circular cylindrical tank. The flow is driven by the spinning bottom disk of tank together with/without central injection and radial uniform-ejection through the sidewall. Numerical solutions of steady and unsteady flows to 3-dimensional Navier-Stokes equation were obtained for several cases of injection strength. In a moderate flow rate of injection, the mass transfer occurs through the boundary layers but, as the flow rate increases, the inner region far from the container walls takes part in mass transfer.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.487-490
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• 2008

A theoretical study is made of the flow in a confined cylindrical container with differential rotating top and bottom disks. Two kinds of theoretical solution for the azimuthal velocity were obtained: one is an exact solution of Bessel function type and the other is an approximate solution of exponential function type which comes from WKB approximation. Both theoretical solutions are shown to be self consistent with each other as well as a good agreement with previous studies. Moreover, in a range of relatively low Reynolds number, the obtained solution of Bessel function type shows better result than previous solutions.

• Wind and Structures
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• 제15권5호
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• pp.355-367
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• 2012

Atmospheric boundary layer winds experience two types of effects due to friction at the ground surface. One effect is the increase of the wind speeds with height above the surface. The second effect, called the Ekman layer effect, entails veering - the change of the wind speed direction as a function of height above the surface. In this study a practical procedure is developed within a database-assisted design (DAD) framework that accounts approximately for veering effects on tall building design. The procedure was applied in a case study of a 60-story reinforced concrete building, which also considered the dependence of veering effects on the orientation of the building. Comparisons are presented between response estimates that do not account for veering, and account for veering conservatively. For the case studied in this paper veering effects were found to be small.

• Wind and Structures
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• 제30권1호
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• pp.69-83
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• 2020

Modelling incompressible, neutrally stratified, barotropic, horizontally homogeneous and steady-state atmospheric boundary layer (ABL) is an important aspect in computational wind engineering (CWE) applications. The ABL flow can be viewed as a balance of the horizontal pressure gradient force, the Coriolis force and the turbulent stress divergence. While much research has focused on the increase of the wind velocity with height, the Ekman layer effects, entailing veering - the change of the wind velocity direction with height, are far less concerned in wind engineering. In this paper, a modified k-ε model is introduced for the ABL simulation considering wind veering. The self-sustainable method is discussed in detail including the precursor simulation, main simulation and near-ground physical quantities adjustment. Comparisons are presented among the simulation results, field measurement values and the wind profiles used in the conventional wind tunnel test. The studies show that the modified k-ε model simulation results are consistent with field measurement values. The self-sustainable method is effective to maintain the ABL physical quantities in an empty domain. The wind profiles used in the conventional wind tunnel test have deficiencies in the prediction of upper-level winds. The studies in this paper support future practical super high-rise buildings design in CWE.

• 한국해양학회지
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• 제18권1호
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• pp.43-48
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• 1983

동계 동해와 황해 표층 수십 메터에서 불안정 성층을 수반한 해양 온도 역전 현상이 종종 발생한다. 수온 역전층 발생의 원인으로서는 (1) 해면으로부터의 열손실을 보상하기 위한 해양 내부의 대류에 기인한 수온 역전, (2) 계절적 수온 변화가 하방으로 전달되면서 진폭과 위상이 바뀜에 따른 동계의 수온 역전, 그리고 (3) 냉수역에서 온수역으로 취송류가 이동함에 따른 수온 역전 등을 들 수 있는 바, 이 논문에서는 위의 세가지 수온 역전 발생 원인에 대하여 해석적인 모델을 제시한다.

• 한국콘텐츠학회논문지
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• 제15권5호
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• pp.1-17
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• 2015

국내 게임 업계에서 비디오 게임 시장은 좁아지고 있고 그에 따른 자본과 인력 또한 줄어들고 있다. 이런 열악한 환경과 전문 기술력에서 나오는 콘텐츠의 질적 향상을 위해서는 전문 개발자가 아니더라도 보다 사실적이고 질적으로 뛰어난 콘텐츠를 제작하는 데 도움이 되는 연구가 필요하다. 본 연구에서는 대중과 평론가들에게서 캐릭터 감정 표현 및 전달이 잘 되었다고 평가받는 해외 전문 제작사의 애니메이션들을 선정하였다. 그리고 해당 애니메이션의 스크립트에서 Ekman의 6가지 기본 감정과 그레마스의 역동적 서술어를 이용해 캐릭터가 감정을 표현하는 행동을 선별하여 분석 및 분류하였다. 또한, 게임 제작 프로그램 유니티의 블렌딩 작업에 사용되는 '애니메이션 레이어'를 이용해서 캐릭터가 특정 감정을 표현하려 할 때 필요로 하는 행동들을 분석하고, 이 데이터를 사용해서 감정을 표현하는 행동을 제작해주는 프로그램의 구상안을 제안한다.