• 한국항행학회논문지
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• 제27권4호
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• pp.488-494
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• 2023

본 논문에서는 2차원 침수해석 모형인 G2D를 이용하여 모의 도메인을 구성하고, 전주시 전역을 대상으로 시나리오 기반 도시 침수예측을 수행하였다. 도메인 구성과 격자별 조도계수 설정은 DEM과 토지피복도를 이용하고, G2D 모형의 입력은 수위, 수심 및 유량 등을 적용하였다. 가상강우는10분당3 mm로5시간동안모든격자에부여하였고, 가상 유량을 적용하여 지표면 침수해석 모의를 진행하였다. 또한 대상 지역의 침수해석 모델 실행 여부를 판단하기 위해 GPU 가속기법을 적용하였다. 모의 결과 고해상도 침수해석 시간의 대폭 단축 및 모의 시간별 시각적인 침수 판단을 위한 침수심을 생성할 수 있음을 확인하였다.

• 대한공간정보학회지
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• 제24권3호
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• pp.59-66
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• 2016

2011년 발생한 서울시 우면산의 토석류는 과거 산간지역 피해와는 달리 도심지역에서 큰 피해가 발생하였다. 따라서 산사태 및 토석류는 산악지역과 도심지역에 관계없이 다양한 지역에서 빠른 속도로 발생하여 엄청난 피해를 유발시키기 때문에 많은 연구자들은 토석류의 영향범위를 예측하고 피해를 최소화하기 위해 노력하고 있다. 토석류의 영향범위 예측을 위한 가장 핵심적인 부분은 복잡한 3차원 지형에서의 토석류 거동 및 퇴적 메커니즘을 이해하여야 한다. 그리고 퇴적 메커니즘을 이해하기 위해서는 토석류의 거동에 따른 에너지량과 침식량이 산정되어야 한다. 하지만 기존에 개발된 토석류 모델들은 토석류의 침식량을 산정하는데 한계가 있었다. 따라서 본 연구에서는 2011년 도심지의 대규모 토석류가 발생한 서울시 우면산 지역을 대상으로 항공사진, 항공 LiDAR 자료로부터 생성된 토석류 피해 전과 후의 DEM을 활용하여 토석류의 피해규모를 산정하였으며, 에너지 이론을 기반으로 하여 침식량을 산정할 수 있는 토석류 거동 해석 모델을 개발하여 비교하였다. 또한 동일지역에 대하여 기존의 토석류 모델(RWM, Debris 2D)도 함께 시뮬레이션 하여 종합적으로 토석류 지역을 비교 분석하였다.

• Journal of Electrochemical Science and Technology
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• 제10권4호
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• pp.408-415
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• 2019

Electroplating is a widely used surface treatment method in the manufacturing process of electronic parts and uniformity of the electrodeposition thickness is very crucial for these applications. Since many variables including fluid flow influence the uniformity of the film, it is difficult to conduct efficient research only by experiments. So many studies using simulation have been carried out. However, the most popular simulation technique, which calculates secondary current distribution, has a limitation on the considering the effects of fluid flow on the deposition behavior. And modified method, which is calculating a tertiary current distribution, is limited to a two-dimensional study of simple shapes because of the massive computational load. In the present study, we propose a new electroplating simulation method that can be applied to complex shapes considering the effect of flow. This new model calculates the electroplating process with three steps. First, the thickness of boundary layers on the surface of the cathode plane and velocity magnitudes at the positions are calculated from the simulation of fluid flow. Next, polarization curves of different velocities are obtained by calculations or experiments. Finally, both results are incorporated into the electroplating simulation program as boundary conditions at the cathode plane. The results of the model showed good agreements with the experimental results, and the effects of fluid flow of electrolytes on the uniformity of deposition thickness was quantitatively predicted.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.45-49
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• 2007

Asymmetric force and vibration caused by separation flow at high angle of attack affect the stability of supersonic missile. As a preliminary study we verified the effect of turbulence model through general 3-D slender body for the supersonic flow at high angle of attack. ${\kappa}-{\omega}$ Wilcox model, ${\kappa}-{\omega}$ Wilcox-Durbin+ model, ${\kappa}-{\omega}$ shear-stress transport model, and Spalart-Allmaras one equation model are used. Grid sensitivity test was performed with three different grid system. results show that all models are in good agreement with the experimental data.

• 한국방재안전학회논문집
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• 제16권4호
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• pp.9-18
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• 2023

기후변화는 외수침수와 연관이 있는 하천제방 안전성에도 영향을 미친다. 제방의 안전성을 높이기 위해 비탈면 보강에 대한 연구가 활발히 수행되어왔다. 특히 최근에는 순환자원을 재활용하여 호안블록을 제작하는 기술 등이 개발되고 있다. 그러나 호안블록의 재료적인 측면의 연구와 더불어 블록 형상에 의해 제외지의 흐름특성에 미치는 영향을 분석하는 것이 필요하다. 따라서 본 연구에서는 호안블록의 형상에 따라 호안면의 유속 등 수리학적 특성의 영향을 3차원 수치모의를 통해 수행하였다. 호안 블록 형상은 3가지 형상을 제안하였고, 이상적인 하천 수로에 블록을 설치하여 수치해석을 수행하였다. 3차원 수치해석은 FLOW-3D를 사용하였고, 호안블록의 형상에 따른 최대유속, 호안부의 바닥유속, 최대 전단응력의 변화를 분석하였다. 그 결과, 자연석형 식생블록인 블록 A가 요철의 크기와 규모가 불규칙하여 호안에 연결하여 설치할 경우 호안 블록 B, C보다 호안 설치구간의 유속변화가 가장 큰 것으로 분석되었다. 향후 하천의 지형적 특성을 고려한다면 현장적용성을 고려한 호안블록 설계를 수행할 수 있을 것으로 기대된다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2003년도 추계학술발표대회 요약집
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• pp.95.1-95.1
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• 2003

• Wind and Structures
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• 제23권6호
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• pp.505-521
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• 2016

The objective of this study is to investigate numerically the effect of building roof shaps on wind flow and pollutant dispersion in a street canyon with one row of trees of pore volume, $P_{vol}=96%$. A three-dimensional computational fluid dynamics (CFD) model is used to evaluate air flow and pollutant dispersion within an urban street canyon using Reynolds-averaged Navier-Stokes (RANS) equations and the Explicit Algebraic Reynolds Stress Models (EARSM) based on k-${\varepsilon}$ turbulence model to close the equation system. The numerical model is performed with ANSYS-CFX code. Vehicle emissions were simulated as double line sources along the street. The numerical model was validated by the wind tunnel experiment results. Having established this, the wind flow and pollutant dispersion in urban street canyons (with six roof shapes buildings) are simulated. The numerical simulation results agree reasonably with the wind tunnel data. The results obtained in this work, indicate that the flow in 3D domain is more complicated; this complexity is increased with the presence of trees and variability of the roof shapes. The results also indicated that the largest pollutant concentration level for two walls (leeward and windward wall) is observed with the upwind wedge-shaped roof. But the smallest pollutant concentration level is observed with the dome roof-shaped.

• 한국물환경학회지
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• 제24권3호
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• pp.365-377
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• 2008

Large artificial dam reservoirs and associated downstream ecosystems are under increased pressure from long-term negative impacts of turbid flood runoff. Despite various emerging issues of reservoir turbidity flow, turbidity modeling studies have been rare due to lack of experimental data that can support scientific interpretation. Modeling suspended sediment (SS) dynamics, and therefore turbidity ($C_T$), requires provision of constitutive relationships ($SS-C_T$) and accounting for deposition of different SS size fractions/types distribution in order to display this complicated dynamic behavior. This study explored the performance of a coupled two-dimensional (2D) hydrodynamic and particle dynamics model that simulates the fate and transport of a turbid density flow in a negatively buoyant density flow regime. Multiple groups of suspended sediment (SS), classified by the particle size and their site-specific $SS-C_T$ relationships, were used for the conversion between field measurements ($C_T$) and model state variables (SS). The 2D model showed, in overall, good performance in reproducing the reservoir thermal structure, flood propagation dynamics and the magnitude and distribution of turbidity in the stratified reservoir. Some significant errors were noticed in the transitional zone due to the inherent lateral averaging assumption of the 2D hydrodynamic model, and in the lacustrine zone possibly due to long-term decay of particulate organic matters induced during flood runoffs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제2권2호
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• pp.120-133
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• 2008

This paper presents a novel approach for facial motion tracking and facial expression cloning to create a realistic facial animation of a 3D avatar. The exact head pose estimation and facial expression tracking are critical issues that must be solved when developing vision-based computer animation. In this paper, we deal with these two problems. The proposed approach consists of two phases: dynamic head pose estimation and facial expression cloning. The dynamic head pose estimation can robustly estimate a 3D head pose from input video images. Given an initial reference template of a face image and the corresponding 3D head pose, the full head motion is recovered by projecting a cylindrical head model onto the face image. It is possible to recover the head pose regardless of light variations and self-occlusion by updating the template dynamically. In the phase of synthesizing the facial expression, the variations of the major facial feature points of the face images are tracked by using optical flow and the variations are retargeted to the 3D face model. At the same time, we exploit the RBF (Radial Basis Function) to deform the local area of the face model around the major feature points. Consequently, facial expression synthesis is done by directly tracking the variations of the major feature points and indirectly estimating the variations of the regional feature points. From the experiments, we can prove that the proposed vision-based facial expression cloning method automatically estimates the 3D head pose and produces realistic 3D facial expressions in real time.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.243-248
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• 2007

A three-dimensional (3D) unstructured hydrodynamic solver for transient two-phase flows has been developed. A two-fluid three-field model was adopted for the two-phase flows. The three fields represent a continuous liquid, an entrained liquid, and a vapour field. The hydrodynamic solver is for the 3D component of a nuclear system code and the component-scale analysis tools for transient two-phase flows. The finite volume method and unstructured grid are adopted, which are useful for the flows in a complicated geometry. The semi-implicit ICE (Implicit Continuous-fluid Eulerian) numerical scheme has been adapted to the unstructured non-staggered grid. This paper presents the numerical method and the preliminary results of the calculations. The results show that the numerical scheme is robust and predicts the phase change and the flow transitions due to boiling and flashing problems well.