• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.701-704
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• 2005

Aquifer Thermal Energy Storage (ATES) can be a cost-effective and renewable geothermal energy source, depending on site-specific and thermohydraulic conditions. To design an effective ATES system having influenced by groundwater movement, understanding of thermo hydraulic processes is necessary. The heat transfer phenomena for an aquifer heat storage are simulated using FEFLOW with the scenario of heat pump operation with pumping and waste water reinjection in a two layered confined aquifer model. Temperature distribution of the aquifer model is generated, and hydraulic heads and temperature variations are monitored at the both wells during 365 days. The average groundwater velocities are determined with two hydraulic gradient sets according to boundary conditions, and the effect of groundwater flow are shown at the generated thermal distributions of three different depth slices. The generated temperature contour lines at the hydraulic gradient of 0.00 1 are shaped circular, and the center is moved less than 5m to the groundwater flow direction in 365 days simulation period. However at the hydraulic gradient of 0.01, the contour center of the temperature are moved to the end of boundary at each slice and the largest movement is at bottom slice. By the analysis of thermal interference data between two wells the efficiency of the heat pump system model is validated, and the variation of heads is monitored at injection, pumping and no operation mode.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.115-118
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• 2002

The present study deals with CFD analysis of a plastic heat exchanger with corrugated wall. This exchanger has sinusoidal corrugations, and the flow through the exchanger is three dimensional. In addition, CFX-5.4, a commercial code utilizing unstructured mesh, was used as a computational method for solving RANS(Reynolds-Averaged Navier-Stokes) equations, and the applied turbulence model is $k-{\varepsilon}$ model. The factors to affect the efficiency of a plastic heat exchanger are heat conductivity, flow characteristics and so on. For those two factors, heat conductivity is fixed by the wall material. Therefore, the How along the corrugation affects the efficiency more, provided the same material. In conclusion, the heat transfer enhancement of a plastic heat exchanger with corrugated wall can be recognized from the flow characteristics such as velocity streamline, local heat transfer coefficient, velocity contour, and pressure contour. To confirm the results, both of the measured and the computational data for pressure loss were compared with each other, and they were identical.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2845-2850
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• 2007

Flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re =100 were numerically studied. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. It turns out that significant changes in the characteristics of flow-induced forces are noticed depending on how the two circular cylinders are positioned, resulting in quantitative changes of force coefficients on both cylinders. Collecting all the numerical results obtained, we propose a contour diagram for drag coefficient and lift coefficient for each of the two cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use those diagrams to estimate flow-induced forces on two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.

• 대한기계학회논문집B
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• 제31권9호
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• pp.754-763
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• 2007

Flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re=100 were numerically studied. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. It turns out that significant changes in the characteristics of flow-induced forces are noticed depending on how the two circular cylinders are positioned, resulting in quantitative changes of force coefficients on both cylinders. Collecting all the numerical results obtained, we propose a contour diagram for drag coefficient and lift coefficient for each of the two cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use those diagrams to estimate flow-induced forces on two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.

• 한국지능시스템학회논문지
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• 제18권2호
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• pp.206-211
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• 2008

영상처리 기술을 이용한 모의훈련에서 사용자는 영상에 전시된 가상객체를 통해 실세계와의 상호작용과 인식능력을 향상시킬 수 있다. 따라서 현실감 있는 모의훈련을 위해서는 가상객체와 실영상을 정합한 후 가상객체로 인해 생기는 폐색영역을 결정하는 것이 필수적이다. 본 논문에서는 실 영상위에서 지정된 경로에 따라 가상표적을 이동시킬 때 발생하는 폐색문제를 이웃에지 탐색을 이용한 개선된 윤곽선 추출 알고리즘과 MER(Minimum Enclosing Rectangle)을 이용하여 해결한다. 제안된 윤곽선 추출 알고리즘에 의해 복잡한 물체에 대한 세부적인 윤곽을 얻은 후 성능향상을 위해 객체의 MER을 이용하여 폐색이 일어나는 지점의 3차원 정보를 산출하였다. 실험에서는 부분적 폐색이 발생하는 환경에서 제안한 방법을 기존방법과 비교하고 유효성을 입증하였다.

• Journal of the Korean Data and Information Science Society
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• 제18권2호
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• pp.439-445
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• 2007

GVF can solve two difficulties with Snakes that are on setting initial contour and have a hard time processing into boundary concavities. But GVF takes much longer computation time than the existing Snakes because of their edge map and partial derivatives. Therefore this paper analyzed the computation time between GVF and Snakes. As a simulation result, both algorithms took almost similar computation time in simple image. In real images, GVF took about two times computation than Snakes.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.681-686
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• 2007

The flow analysis was made by applying the turbulent models in the scroll volume of centrifugal compressor. The $k-{\varepsilon}.\;k-{\omega}$, Spalart-Allmaras and reynolds stress models are used in which the hybrid grid is applied for the simulation. The velocity vector the Pressure contour. the change of residual along the iteration number. and the dynamic head are simulated by solving the Navier-Stokes equations for the comparison of four example cases.

• 대한기계학회논문집B
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• 제32권1호
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• pp.30-38
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• 2008

As a follow-up of our previous studies on flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re=100 and flow patterns past them,$^{(1,2)}$ we present Reynolds-number effects on the forces and patterns by further computing flows with Re=40, 50, 160. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the angle inclined with respect to the main flow direction. Collecting all the numerical results obtained, we propose contour diagrams for mean force coefficients and their rms of fluctuation as well as for flow patterns and Strouhal number for each Re. These diagrams shed light on a comprehensive picture on how the wake interaction between the two cylinders alters depending on Re.

• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.437-446
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• 2003

A large eddy simulation (LES) is performed for turbulent pipe flow. The simulation code is constructed by using a general coordinate system based on the physical contravariant velocity components. The effects of grid fineness which can be well prediction of turbulent behavior in near wall region is investigated. The subgrid scale turbulent models are applied and validated emphasis is placed on the flow details of turbulent pipe flow The calculated Reynolds number is 360 based on the wall shear velocity and the inlet pipe diameter. The predicted turbulent statistics are evaluated by comparing with the DNS data of turbulent pipe flow Performed by Eggels et al. The agreement of LES with DNS data is shown to be satisfactory. The proper grid fineness of the well prediction of turbulent pipe flow is suggested and the turbulent behavior is analyzed by depict the contour plot of fluctuating velocity components.

• 대한공간정보학회지
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• 제15권2호통권40호
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• pp.59-66
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• 2007

최근 들어 디지털 기반의 산업환경 변화와 더불어 관련 기술의 변화가 급속히 진행되고 있다. 측량분야에서도 과거 단순히 항공사진을 이용하여 도화를 하던 방식에서 벗어나 GPS 및 INS 등의 멀티센서 및 디지털 카메라를 이용한 디지털 방식의 작업환경이 도입되고 있다. 지형에 대한 정확한 데이터는 국토의 효율적 이용 및 관리, 도시계획 수립, 환경 및 재난관리 등 여러 분야에서 광범위하게 활용되고 있으며 지식정보시대의 필수적인 정보인프라로 인식되고 있다. 본 연구에서는 수목 등에 투과성이 우수하며 비행설계에서부터 최종성과물까지 디지털 방식으로 정확 신속하게 데이터를 산출할 수 있는 항공레이저측량을 이용하여 지형정보를 취득하였으며, 이를 통해 제작된 등고선과 항공사진 도화에 의한 현행 수치지형도(1/1,000 및 1/5,000의 등고선을 비교하여 그 정확도와 세밀도 및 경제적 관점에서 효율성을 평가하였다. GPS측량에 의한 정확도 평가 결과, LiDAR 데이터의 표고 정확도는 평균 $0.089m{\pm}0.062m$로써 1/1,000 수치지형도보다 우수하게 나타났으며, 복잡한 도시의 지물을 보다 더 세밀하게 표현할 수 있었다. 경제적 측면에서는 현행 항공사진 도화에 의한 1/1,000 수치지형도 등고선 제작비용($100km^2$ 기준)과 비교하여 약 48%의 비용절감 효과를 나타냈다. 본 연구결과, 갱신주기가 수년에 이르는 수치지형도의 수정 갱신이 미흡한 현재의 상태에서 항공레이저측량에 의하여 획득된 LiDAR 데이터를 이용할 경우에 등고선의 최신성 및 현시성을 충족시킬 수 있는 대안임을 보여 주었다.