• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.3
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• pp.29-36
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• 2002

A numerical analysis based on two-dimensional and three-dimensional incompressible Wavier-Stokes equations has been carried out for double-circular-arc compressor cascades and the results are compared with available experimental data at various incidence angles. The 2-D and 3-D computational codes based on SIMPLE algorithm adopt pressure weighted interpolation method for non-staggered grid and hybrid scheme for the convective terms. Turbulence modeling is very important for prediction of cascade flows, which are extremely complex with separation and reattachment by adverse pressure gradient. Considering computation times, $\kappa$-$\varepsilon$ turbulence model with wall function is used.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.14 no.2
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• pp.159-166
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• 1996

It has the imfortant significance to study of 3 dimensional precision surveying and analysis system for conservation of culutral properties. This study is about to efficient precision surveying methods and analysis of digital information data for conservation of cultral properties. We acquire the photos and construct the 3 dimensional digital information in 1 n accuracy, and carry the spatial analysis to five story pagoda at Chongrimsa temple site of National Treasure No. 9 of Korea. In result, we carry the 3 dimensional modelling accurately and the efficient geometrical analysis of sections, calculation of the aera, volumn, and position and slope of con-trial axis. So, we expect efficient use of as well study of art history as safety diagonise for the preservation of cultural properties.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.217-224
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• 2007

Tunnel displacement happens during the process of stress redistribution by tunnelling. Tunnel displacement can be divided into 3 types such as displacements occurring before excavation, non-measured displacements after excavation and measured displacements after excavation. Because measurements of displacements occurring before excavation and non-measured displacement after excavation are difficult and time-consuming in the field, many researchers have studied on total displacement and its characteristics with excavation using numerical analysis. In this study, we used a 3-D back analysis to estimate total displacement by rock mass grades in tunnel constructed in sedimentary rock. We reduced error between measured displacements and calculated displacements from a 3-D numerical analysis, and then estimated suitable rock mass properties by RMR classes. Ultimately, Logistic nonlinear regressions of total displacement with tunnelling were estimated by least square estimation.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2109-2110
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• 2006

유한요소법은 전자기, 기계, 또는 다른 공학 분야에서 다루는 풀기 어려운 복잡한 문제들을 해석하는데 널리 사용되고 있는 수치해석기법이다. CEMTool은 MATLAB과 유사한 과학기술 범용 패키지로서, 간편한 명령어 방식의 문법과 블록 다이어그램 설계, 이공학 전반의 함수 등의 다양한 기능들을 제공한다. 본 논문에서는 범용 공학 소프트웨어인 CEMTool 환경에서 실행되는 GUI 3D FEM 패키지에 대해 기술한다. FEM 해석의 일반적 단계인 전처리, 솔버, 후처리 단계별로 나누어 각 단계의 구조와 특징 등을 기존의 CEMTool 2D FEM 패키지, MATLAB PDE Toolbox, FEMLAB2.2와 비교하여 자세히 살펴보기로 한다.

• Journal of Energy Engineering
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• v.6 no.2
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• pp.137-144
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• 1997

Turbulent swirling cold-flow in a cyclonic gasifier has been analyzed by numerical analysis. Comparison of two dimensional and three dimensional analyses has shown that concept of equivalent slit is appropriate for the two dimensionalization of three dimensional phenomena. Flow characteristics have been scrutinized by varying swirl number which is a crucial parameter in determining the flow pattern of the cyclonic gasifier. Reactive flow field has been estimated by using theoretical swirl number and equivalent slit width for reactive flow. Results show that proper flow field for the reactive coal gasification can be formed by controlling the exit area and azimuthal location of coal burners.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.35-40
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• 2002

A numerical analysis based on two-dimensional and three-dimensional incompressible Navier-Stokes equations has been carried out for double-circular-arc compressor cascades and the results are compared with available experimental data at various incidence angles. The 2-D and 3-D computational codes based on SIMPLE algorithm adopt pressure weighted interpolation method for non-staggered grid and hybrid scheme for the convertive terms. Turbulence modeling is very important for prediction of cascade flows, which are extremely complex with separation and reattachment by adverse pressure gradient. In this paper k-$\varepsilon$ turbulence model with wall function is used to increase efficiency of computation times.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.719-727
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• 2008

A 3-D compressible Navier-Stokes solver using overlapped grids is developed to predict a flow-field around a hovering rotor. The flow solver is verified by a parametric study with the grid spacing of wake grid, spatial accuracy and turbulence model. Computations are performed with different Chimera grid systems. Computational results are compared with the experimental data of Caradonna et al. for both blade loading and the tip vortex behavior. Numerical results show good agreements with experiments for the distribution of surface pressure and tip vortex behavior. Pressure distributions over the blade have marginal differences for different numerical methods, whereas large discrepancies are seen in the prediction of the wake behavior. Results unexpectedly show that the vortex strength from an automated cut-paste Chimera grid is weaker than that from the conventional Chimera grid.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.244-244
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• 2021

난류흐름 거동은 지형이나 수공구조물과 같은 고체 경계면의 변화에 민감하게 반응하며 특징 또한 다양하다. 보나 여수로 등과 같은 단차 구조물을 통과하는 흐름은 구조물의 모서리 같은 흐름 경계면이 급변하는 지점에서는 흐름분리(flow separation)가 발생하는 것이 특징이다. 이러한 흐름분리로 인해 전단층이 발생하며 흐름 재순환(recirculation)이 구조물 하류부에 형성된다. 이 연구에서는 낙차공 형식의 단차 구조물 하류부에서의 흐름 거동을 이해하기 위해 CFD모델링을 통하여 계산된 3차원 유동장을 분석한다. 난류 모의는 하이브리드 LES(large-eddy simulation)/RANS 계산 기법인 IDDES(improved delayed detached-eddy simulation)기법을 적용한다. IDDES의 기본 모형으로는 k-ω SST모형과 Spalart-Allmaras모형을 이용하여 두 모형의 성능을 평가한다. 자유수면의 변동은 VoF(volume of fluid)기법을 이용하여 계산하며, 각 지배방정식은 최소의 수치분산을 유지하면서 수치해의 안정성을 확보할 수 있는 2차 정확도의 유한체적법을 이용하여 이산화하였다. 수치해석 결과는 레이놀즈수 23,400과 후르드수 0.22의 조건에서 기존에 계측된 자료와 비교하여 수치모형의 정확도를 평가하고 하상 단차 하류부에서의 흐름 거동 특성을 분석한다. 계산 결과는 공학적으로 널리 사용되는 RANS 수치모의에서 볼 수 없는 전단층과 난류구조의 동적 거동 특성과 이에 따른 레이놀즈 응력분포의 특성을 설명해준다.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.225-234
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• 1995

터빈익렬내부의 유동해석을 위해 비압축성 점성유동해석을 이용한 수치 해석 프로그램을 개발하였다. 지배방정식으로는 2차원의 비정상 비압축성 Navier-Stokes 방정식을 일반화된 곡선좌표계로 전환하여 암시적으로(implicitly) 반복적인 시간진행방법을 이용하여 유동해석을 하였다. 지배방정식의 각항들은 시간에 대해 1차의 정확도 그리고 영역에 대해서는 2차의 정확도, 대류항에 대해서는 3차의 정확도를 가지는 Upwind기법을 적용하였다. 특히, 실험적 접근이 매우 어려운 터빈의 정익과 회전하고 있는 동익과의 상호운동을 멀티블럭기법과 데이터 interface를 통해 보다 쉽게 해석할 수 있었다. 본 연구결과는 정익만을 계산한 타 연구자의 결과와의 비교시 매우 일치하였으며 물리적인 유동을 잘 파악할 수 있었다. 난류유동 해석을 위해서 Baldwin-Lomax 모델을 적용하였다.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.365-374
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• 2003

This is a study on application of a TVD-Mccormack scheme for the computation of one-dimensional dam-break flows. The TVD scheme not only has the ability to damp out oscillations, but also does not contain terms with adjustable parameters. Moreover, the TVD-McCormack scheme does not cause any additional difficulty when dealing with the source term of the equation and retains second-order accuracy in both space and time. In this study, by appropriately designing the limiter functions, the TVD property can be achieved, and numerical oscillations near a jump discontinuities can be eliminated or reduced. Also, this numerical scheme has less computational errors when the direction of the predictor-corrector step is in the same direction as the shock wane propagation.