• Spatial Information Research
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• 제17권3호
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• pp.389-395
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• 2009

토석류에 대한 많은 수치 해석적 연구에도 불구하고 아직 일관된 연구 결과는 없는 실정이다. 따라서 본 연구에서는 강우 유출 모형을 적용하기 위해 소유역별 대상유역을 분할하고 토석류 입자와 유체를 일체화한 토석류 유출량을 산정하고자 하였다. 등고선 데이터를 이용하여 소유역 하도망과 같은 유역의 지형량을 자동적으로 도출하였으며, 준 수치고도모델(Quasi Digital Elevation Model)을 모형화함으로써 강우 유출량을 해석하였다. 계측된 토석류 자료와 강우자료를 입력하여 토석류 모형을 통합화하였으며 이를 적용한 결과 대체로 토석류 유출과 유사한 하이드로 그래프를 얻을 수 있었으며 유의한 점으로써 토석류는 30초 이내에 유출되므로 피해를 최소화하기 위해서는 사전적 대응이 중요함을 시사한다. GIS와 연계한 본 모형은 향후 토석류 유출에 따른 유역별 하천계획의 수립시 유효한 자료를 제공할 것으로 기대한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.661-667
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• 2001

This paper is concerned with the effects of periodically approaching upstream wakes on cascade-flow and loss. The reduced frequency of the periodic wakes was varied in the narrow range from 0.5 to 0.7. According to a wake-passing through the cascade, two velocity deficits appear near the boundary layer contour in the downstream from about 60% chord-length. The first velocity deficit is caused by a periodic wake and the second one appears after some delayed time. The second velocity deficit may be interpreted as the results of reattachment of flow-separation. The higher reduced frequency decreases the duration time of separation appearance and the lesser loss of aerofoil is resulted.

• 대한조선학회지
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• 제27권2호
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• pp.40-46
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• 1990

이산 보오텍스를 내포하고 있는 이상유체의 비정상 유동에 의하여 원주에 작용되는 양력과 항력을 계산하기 위한 수식을 유도하였다. 이 식은 유체유동에 대한 시뮬레이션에서 이산 보오텍스법을 적용할 때 사용될 수 있으며 복소평면 위에서 연결선 적분에 의하여 유도되었다. Sarpkaya의 공식과는 의미에 상당한 차이가 있는 항이 나와 있어 지금까지 얻어진 힘의 크기에 변화를 초래할 것으로 예상된다.

• 한국전산유체공학회지
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• 제9권2호
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• pp.1-10
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• 2004

In the present study, a post-processing program is developed for 3D data visualization and analysis. Because the graphical user interface(GUI) of the program is based on Qt-library while all the graphic rendering is performed with OpenGL library, the program runs on not only MS Windows but also UNU and Linux systems without modifying source code. The structure of the program is designed according to the object-oriented programming(OOP) concept so that it has extensibility, reusability, and easiness compared to those by procedural programming. The program is organized as modules by classes, and these classes are made to function through inheritance and cooperation which is an important and valuable concept of object-oriented programming. The major functions realized so far which include mesh plot, contour plot, vector plot, streamline plot, and boundary plot are demonstrated and the relevant algorithms are described.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2009년도 학술발표회 논문집
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• pp.73-82
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• 2009

터널외곽에 적용하는 지발뇌관의 시차 정밀도 차이가 터널의 여굴 형성에 어떠한 영향을 미치는가를 알아보기 위하여 Particle Flow Code 2D (PFC2D)라는 개별요소법을 기반으로 하여 개발된 상용프로그램(Itasca CG, 2004)을 사용하여 분석하였다. 그 결과 시차 정밀도가 정확하면 정확하지 않은 것보다 모암의 손상 및 여굴이 감소하는 것으로 나타났다.

• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.66-78
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• 2007

A multi-point aerodynamic shape optimization technique has been developed for helicopter rotor blades in hover based on a continuous adjoint method on unstructured meshes. The Euler flow solver and the continuous adjoint sensitivity analysis were formulated on the rotating frame of reference. The 'objective function and the sensitivity were obtained as a weighted sum of the values at each design point. The blade section contour was modified by using the Hicks-Henne shape functions. The mesh movement due to the blade geometry change was achieved by using a spring analogy. In order to handle the repeated evaluation of the design cycle efficiently, the flow and adjoint solvers were parallelized based on a domain decomposition strategy. A solution-adaptive mesh refinement technique was adopted for the accurate capturing of the wake. Applications were made to the aerodynamic shape optimization of the Caradonna-Tung rotor blades and the UH-60 rotor blades in hover.

• 대한기계학회논문집B
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• 제33권7호
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• pp.469-476
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• 2009

Most material of engineering interest undergoes solidification process from liquid state. Identifying the underlying mechanism during solidification process is essential to determine the microstructure of material thus the physical properties of final product. In this paper, effect of fluid convection on the dendrite solidification morphology is studied using Level Contour Reconstruction Method. Sharp interface technique is used to implement correct boundary condition for moving solid interface. The results showed good agreement with exact boundary integral solution and compared well with other numerical techniques. Effects of Peclet number and undercooling on growth of dendrite tip of both single and multiple seeds have been also investigated.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.416-419
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• 2006

Numerical analysis is carried out to identify the wall thinning effect inside the feed water valve. The finite volume method is applied to make analysis for the viscous flows. The commercial cock FLUENT is used for the simulation and the GAMBIT for the grid generation. The RNG $\kappa-\varepsilon$ model is used for the turbulence and the tet-hybrid grid is applied for the modeling. The velocity vector, the pressure contour, the change of residual along the iteration number, and the dynamic head are predicted for the hydrodynamic investigation.

• 대한기계학회논문집B
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• 제21권4호
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• pp.503-508
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• 1997

The change of the structure of homogeneous turbulence subject to irrotational strains has been studied in an anti-Morel type diffuser (center matched cubic contour) using the hot wire anemometry. It was observed that the profiles of mean velocities and turbulence velocities along the center line were stable at the entrance region but rapidly changed near the matching point. The wall induced turbulence at the entrance region grows fast and was diffused toward the center at downstream. It was also observed that the axial turbulence grows faster than the radial one in the middle region of the diffusing flow and that the diffusing process has the vortex compression mechanism due to the conservation of angular momentum. These phenomena are frequently observed at the initial flow region of the free jet.

• 한국기계가공학회지
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• 제15권2호
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• pp.9-15
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• 2016

The dynamics of gas-particle flow from a supersonic abrasive blasting nozzle have been studied by 1-D analytical calculation, including wall friction effects inside the nozzle. The developed code in the present study shows a satisfactory agreement with the other study's results. By utilizing the code, the redesign and optimization of the inner contour of a commercial abrasive blasting nozzle were carried out, and it was found that the redesigned nozzle in the present study can produce faster particle velocities at the nozzle exit by up to 22% compared with the original commercial nozzle.