• Ecology and Resilient Infrastructure
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• 제6권4호
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• pp.328-338
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• 2019

본 논문에서는 하천의 지류와 본류가 만나는 합류부를 대상으로 2차원 수치모형인 CCHE2D를 이용하여 장래하상변동 수치모의를 수행하고 분석을 수행하였다. 대상구간은 하상변동의 개연성이 클 것으로 예상되는 낙동강과 감천 합류부 그리고 금강과 미호천 합류부를 대상으로 하였다. 해당구간에서 4대강 살리기 사업이 종료된 이후인 2012년 8월 30일부터 2015년 8월 29일 수문자료를 활용하여 장래하상변동 수치모의를 수행하였다. 장래하상변동 수치모의 결과 합류부 부근에서 하상변동이 활발히 발생하는 것으로 나타났으며 특히 유사 퇴적이 집중되어 사주가 형성될 가능이 있는 것으로 나타났다. 수치모의를 통해 대상구간에서 하상변동, 평균 하상고 변화, 세퇴차량 등을 검토하여 장래 하도변화 특성을 검토하였다. 2차원 수치모형을 활용하여 지류 합류부 구간에서 향후 효율적인 지류 합류부 하도안정화 대책을 수립하는데 활용될 것으로 기대된다.

• 한국수자원학회논문집
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• 제56권1호
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• pp.23-34
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• 2023

본 연구에서는 실내실험과 수치모의를 통해 식생대에서의 소류사 이동 및 하도 변화를 분석하였다. 실내시험에서 식생대의 영향을 검토하기 위해 아크릴 봉으로 제작한 인공 식생대를 실험수로에 설치하였으며, 유량 조건을 조정하여 유량변화에 따른 식생대에서의 소류사 이동 및 하도 변화를 검토하였다. 다음으로 실내실험과 동일한 조건을 2차원 수치 모형인 Nays2D모형에 적용하여 수치모의를 수행하고, 그 결과를 실내실험 결과와 비교하여 수치모형의 적용성을 검토하였다. 마지막으로 적용성을 검토한 수치모형을 적용하여 식생밀도의 변화에 따른 소류사 이동 및 하도의 변화를 검토하였다. 실내실험과 수치모형을 적용하여 유량변화에 따른 식생대에서의 소류사 이동 및 하도 변화를 검토한 결과, 두 적용 방법의 결과가 유사하게 나타났다. 유량이 증가함에 따라 상류에서 유입된 소류사가 식생대 내부에 퇴적되었으며, 식생대 반대편에는 흐름이 집중되어 침식이 발생하였다. 또한 시간이 지날수록 하류방향으로 침식범위가 증가하였다. 식생밀도의 변화에 따른 소류사 이동 및 하도의 변화를 검토한 결과, 식생대의 식생밀도가 증가할수록 상류에서 유입된 소류사가 식생대 내부에 퇴적되었다. 또한 식생밀도의 증가로 인하여 흐름이 식생대의 반대편으로 집중되어 식생대 반대편 하도의 침식이 발생하였다.

• 한국항공운항학회:학술대회논문집
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• 한국항공운항학회 2004년도 추계학술발표대회 논문집
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• pp.240-246
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• 2004

For the prediction on the onset of oblique shock wave-induced vortex breakdown, computational studies on the Oblique Shock wave/Vortex Interaction (OSVI) are conducted and compared with both experimental results and analytic model. A Shock-stable numerical scheme, the Roe scheme with Mach number-based function (RoeM), and a two-equation eddy viscosity-transport approach are used for three-dimensional turbulent flow computations. The computational configuration is identical to available experiment, and we attempt to ascertain the effect of parameters such as a vertex strength, streamwise velocity deficit, and shock strength at a freestream Mach number of 2.49. Numerical simulations using the ${\kappa}-{\omega}SST$ turbulence model and suitably modeled vortex profiles are able to accurately reproduce many fine features through a direct comparison with experimental observations. The present computational approach to determine the criterion on the onset of oblique shock wave-induced vortex breakdown is found to be in good agreement with both the experimental result and the analytic prediction.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.590-595
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• 2008

In the present paper, the impact damage behavior of steel plate reinforced concrete panels exposed to shock impulsive loading and fragment impact loading is investigated. To evaluate the retrofit performance of a steel-strengthened concrete panels, a numerical experiment using a numerical simulation with AUTODYN, an explicit analysis program is introduced because a real explosion experiment requires the vast investment and expense for facilities as well as the deformation mechanisms are too complicated to be reproduced with a conventional closed-form analyses. The model for the analysis is simplified and idealized as a two-dimensional and axisymmetric case controled with geometry, boundary condition and material properties in order to obtain a resonable computation time. As a result of the analysis, panels subject to either shock loading or fragment loading without the steel plate reinforcement experience the perforation with spalled fragments. In addition, the panels reinforced with steel plate can prevent the perforation and provide the good mechanical effect such as the increase of global stiffness and strength through the composite action between the concrete slab and the steel plate.

• 한국대기환경학회지
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• 제23권2호
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• pp.214-224
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• 2007

A three-dimensional computational fluid dynamics (CFD) model with the renormalization group (RNG) $k-{\varepsilon}$ turbulence model is used to examine the effects of difference in building height on flow and pollutant dispersion in asymmetric street canyons. Three numerical experiments with different street canyons formed by two isolated buildings are performed. In the experiment with equal building height, a portal vortex is formed in the street canyon and a typical recirculation zone is formed behind the downwind building. In the experiment with the downwind building being higher than the upwind building, the ambient flow comes into the street canyon at the front of the downwind building and incoming flow diverges strongly in the street canyon. Hence, pollutants released therein are strongly dispersed through the lateral sides of the street canyon. In the experiment with the upwind building being higher than the downwind building, a large recirculation zone is formed behind the upwind building, which is disturbed by the downwind building. Pollutants are weakly dispersed from the street canyon and the residue concentration ratio is largest among the three experiments. This study shows that the difference in upwind and downwind building height significantly influences flow and pollutant dispersion in and around the street canyon.

• 한국지반신소재학회논문집
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• 제18권3호
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• pp.23-32
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• 2019

본 연구에서는 실내실험 및 수치해석을 통해 무보강 및 보강 조건에 따른 인공어초의 세굴 특성을 알아보았다. 해저 지반 보강재로는 지오그리드(geogrid)를 이용하였으며, 보강 면적은 인공어초 하부 면적 대비 1배, 3배 및 5배와 같이 다양한 배율로 적용하였다. 2차원 흐름 수조 실험을 통해 모래 및 실트 지반에서 인공어초의 세굴 패턴을 알아보았으며, 실내실험과 동일한 조건으로 수치해석을 수행하여 유속 벡터 분포 및 세굴 패턴을 알아보았다. 실내실험과 수치해석을 비교한 결과 세굴 패턴은 전반적으로 유사한 경향을 띄었으며, 무보강 지반보다 보강재를 설치한 인공어초 지반에서 세굴이 감소하는 것으로 나타났다.

• 반도체디스플레이기술학회지
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• 제3권3호
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• pp.19-21
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• 2004

This paper presents a 3-dimensional diffusion simulation with adaptive solution strategy. The developed diffusion simulator VLSIDIF-3 was designed to re-refine areas. Refine scheme was calculated by the difference of doping concentration between any of two nodes. Each element is greater than tolerance and redo diffusion process until error is tolerable. Numerical experiment in low doping diffusion problem showed that this adaptive solution strategy is very efficient in both memory and time, and expected this scheme would be more powerful in complex diffusion model.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2004년도 춘계학술대회 발표 논문집
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• pp.55-58
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• 2004

This paper presents a 3-dimensional diffusion simulation with adaptive solution strategy. The developed diffusion simulator VLSIDIF-3 was designed to re-refine areas where difference of doping concentration between any of two nodes of each element is greater than tolerance and redo diffusion process until error is tolerable. Numerical experiment in low doping diffusion problem showed that this adaptive solution strategy is very efficient in both memory and time, and expected this scheme would be more powerful in complex diffusion model.

• 한국전산유체공학회지
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• 제4권3호
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• pp.35-43
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• 1999

In this study, the shock wave focusing of an elliptic reflector is numerically simulated by solving the Euler equations. The numerical method is the second order upwind TVD scheme with a finite volume discretization. For the verification of the present method, we simulate the moving shock wave passing through a two-dimensional corner. The computed isopycnics are compared with the earlier experiment. Numerical results of the elliptic reflectors show that the density and pressure at the focusing point increase linearly as the aspect ratio of the reflector becomes deep. On the other hand, the gas dynamic focal length decreased with the increase of the reflector aspect ratio.

• 대한기계학회논문집
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• 제15권2호
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• pp.523-536
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• 1991

This dissertation analyzes the running mechanism of flexible and thin tape above rotating head through the numerical simulation and the experiment. The scope of analysis is confined to the phenomena of two dimensional elasto hydrodynamic lubrication between the protruded bump on a rotating cylinder and the running tape. This model is based on the elastic deformation equation of plate and shell and Reynolds equation. Finite difference method is employed as a numerical technique to calculate (1) the distribution of pressure between the running tape and rotating bump and (2) the vertical deformation of elastic thin tape over he rotating bump under hydrodynamic pressure. In numerical analyses, the effects of bump size on flying characteristics of the tape were evaluated and examined considering the influence of tension and stiffness of tape.