• 한국추진공학회지
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• 제15권2호
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• pp.29-35
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• 2011

고체로켓모터 추진제 그레인의 핀-슬롯 표면에서의 연소로 인해 생성된 고온, 고압의 연소가스는 그레인 핀-슬롯 및 내삽노즐을 통해 외부로 방출되면서 형성되는 유동은 매우 복잡하고 다양한 형태를 가진다. 핀-슬롯형 그레인 및 내삽노즐을 가지는 고체로켓모터의 2D, 3D 스케일모델에 대한 공기유동 모사시험을 수행하였으며, 롤토크 발생 등과 같은 내부유동발생 메커니즘을 규명할 수 있는 효과적인 연기-유동장 가시화 기법의 적용방법에 대한 검토가 이루어 졌다. 다양한 광원조사기법 및 촬영장치 방향을 이용하여, 축류 실험모델 노즐 선단부에서의 비대칭 와류튜브에 의한 선회류를 가시화하였다.

• 동력기계공학회지
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• 제17권3호
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• pp.50-56
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• 2013

The analysis of performance characteristics was carried out in the plate type evaporator with counter and parallel flow. To investigate performance of evaporator with water inlet temperature and refrigerant mass flow rate were changed. As a result, when the inlet temperature of water is $8^{\circ}C$, capacity of parallel flow evaporator higher than counter flow is 0.35%. But as the inlet temperature of water rises from $8^{\circ}C$ to $16^{\circ}C$, capacity of counter flow type evaporator higher than parallel flow type is 0.12%, 0.27%, 1.1%, 1.6%, respectively. The findings showed that counter flow type evaporator has a larger capacity than those that were parallel flow type evaporator. As the refrigerant mass flow rate rises, capacity and pressure drop increases in the counter and parallel flow type evaporator.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2002년도 추계 학술대회논문집
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• pp.28-34
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• 2002

A computational study of supersonic flow around lateral jet controlled missile has been performed. For this study, three dimensional Navier-Stokes code(AADL3D) has been developed. Spalart-Allmaras one equation turbulence model has been implemented on the AADL3D code for relatively rapid computational time. For the validation of developed code, AADL3D, pressure distributions on an ogive-cylinder body has been compared with experimental data. Also, the shock structure of sonic jet on the flat plate in the supersonic flow field has been compared with experimental flow visualization result to see the analysis capability of freestream-jet interaction case. A case study has been performed through comparing the normal force coefficient and the moment coefficient of missile body for several jet flow conditions. Current results will be used to the optimum design of a lateral jet controlled missile.

• 한국농공학회지
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• 제43권2호
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• pp.59-68
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• 2001

A water balance analysis was performed for a paddy field neighboring the Dongchang stream, downstream of the Unmun reservoir, which is constructed for the urban water supply. Daily rainfall data were collected and irrigation water flow rate, drainage flow rate, evaportranspiration, infiltration, and piezometeric head were measured in the field. The flow rates were continuously observed by water level logger during the growing season. The evaportranspiration and the infiltration were measured by N-type depletion meter and cylindrical infiltrometer, respectively. PVC pipes with 12mm diameter were used for piezometric head measurement. Total Irrigation and drainage flows were 3,608mm and 1,170mm in 1999, and 3,971mm and 1,548mm in 2000, respectively. The mean and range of the daily infiltration rate were 4.4mm/d and 3.4mm/d to 5.5mm/d in 1999 and 5.1mm/d and 4.1mm/d to 6.5mm/d in 2000, respectively. The net ground water flow including the change of soil water storage was 2,855mm in 1999 and 2,540mm in 2000. The evapotranspiration was 458.3mm in 1999 and 553.5mm in 2000. The range of daily evapotranspiration rate was from 1.6 to 8.7mm/d. The return flow ratio was about 32% in 1999 and 39% in 2000 and three year average was 35% including previous study in 1997. The amount of irrigation water was much higher than design standards or references in this study, This was caused by the inadequate water management practice in the area where water was oversupplied on farmers’ request rather than following sound water management principles.

• 한국전산유체공학회지
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• 제6권3호
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• pp.32-40
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• 2001

Viscous solutions of supersonic jet impinging on a flat plate normal to the flow are simulated using three-dimensional Navier-Stokes solver. The jet impinging flow structure exhibits such complex nature as shock shell, plate shock and Mach disk depending on the flow parameters. Among others, the dominant parameters are the ratio of the nozzle exit pressure to the ambient pressure and the distance between the nozzle exit plane and the impinging plane. In the present study, the nozzle contour and the pressure ratio are held fixed, while the jet impinging distance is varied to illuminate the characteristics of the jet plume with the distance. As the plate is placed close to the nozzle at 3D high, the computed wall pressure at or near the jet center oscillates with large amplitude with respect to the mean value. Here D is the nozzle exit diameter. The amplitude of wall pressure fluctuations subsides as the distance increases, but the maximum mean pressure level at the plate is achieved when the distance is about 4D high. The frequency of the wall pressure is estimated at 6.0 kHz, 9.3 kHz, and 10.0 kHz as the impinging distance varies from 3D, 4D, to 6D, respectively.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2012년도 학술발표회
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• pp.571-575
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• 2012

하구역에서의 대표적인 수리특성인 염수쐐기현상에 대한 정확한 이해는 하구역 수질 및 환경관리 측면에서 필수적인 사항이다. 본 연구에서는 정상염수쐐기 경계층 거동에 대한 실험적 연구결과와 3차원 전산유체역학 프로그램인 FLOW-3D를 이용한 수치모의 결과를 비교해봄으로써 염수쐐기현상에 대한 3차원 수치모형의 적용성을 살펴보았다. FLOW-3D를 이용하여 실험장치의 수로구간을 구성하고 경계조건으로 염수의 수위와 담수의 유량을 입력하였으며 밀도차를 두어 이층류가 발생하도록 모의하였다. 모의결과를 통해 시간평균농도와 표준편차를 무차원화하여 단면별 연직분포를 알아보고 각 단면을 중첩하여 경계층의 거동을 살펴보았으며 염수쐐기길이와 염수심을 무차원화하여 밀도프루드수의 변화에 따른 염수쐐기형상을 살펴보았다. 그리고 각 결과를 기 수행된 실험결과와 비교해 보았다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 춘계 학술대회논문집
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• pp.134-143
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• 2001

Viscous solutions of supersonic jet impinging on a flat plate normal to the flow are simulated using three-dimensional Navier-Stokes solver. The jet impinging flow structure exhibits such complex nature as shock shell, plate shock and Mach disk depending on the flow parameters. Among others, the dominant parameters are the ratio of the nozzle exit pressure to the ambient pressure and the distance between the nozzle exit plane and the impinging plane. In the present study, the nozzle contour and the pressure ratio are held fixed, while the jet impinging distance is varied to illuminate the characteristics of the jet plume with the distance. As the plate is placed close to the nozzle at 3D high, the computed wall pressure at or near the jet center oscillates with large amplitude with respect to the mean value. Here D is the nozzle exit diameter. The amplitude of wall pressure fluctuations subsides as the distance increases, but the maximum pressure level at the plate is achieved when the distance is about 4D high. The frequency of the wall pressure is estimated at 6.0 kHz, 9.3 kHz, and 10.0 kHz as the impinging distance varies from 3D, 4D, to 6D, respectively.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.547-550
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• 2008

A solid rocket motor has quite complex physical condition such exothermal chemical reaction in subsonic area and supersonic ex pansion in a converging-diverging nozzle. To introduce a simulation tool for compressible flow in supersonic range as well as incompressible chemical reaction zone in a whole rocket nozzle is a essential demand. Since the flow vary subsonic to super sonic, the convergence in computation becomes very low and unstable in a whole domain of rocket motor. This paper reports the 2-D Axisymmetric and simple 3-D solid propellant combustion and flow of gases in rocket motor by using a precondi tioning, shear stress turbulence modeling, AUSM(p). To simulate the simplified combustion process, Double base solid propellant is used to calculate reaction of solid propellant.

• 한국습지학회지
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• 제10권2호
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• pp.67-79
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• 2008

하천에서의 부정류 해석을 위해서 1차원 유한차분법(FDM)인 Abbott-Ionescu scheme과 2차원 유한체적법(FVM)인 근사의 Riemann solver(Osher scheme)에 대하여 살펴보았다. 두 모형은 직선 하도, 약간 굽어진 사행하도 및 사행하도에서의 흐름 문제들에 적용되었으며 결과의 비교는 균일한 직사각형 수로에 대하여 이루어졌다. 하천의 복잡한 형상의 표현하기 위해서는 이를 고려할 수 있는 유한체적법을 이용하였다. 유한차분법과 유한체적법 결과는 수위 및 유량 수문곡선에 대하여 매우 만족스러운 것으로 나타났다. 균일한 직선하도에 대해서는 1차원분석으로도 충분하다는 사실을 파악할 수 있었으며, 사행하도의 경우 흐름을 정확하게 모형화하기 위해서는 2차원 또는 3차원 모형을 사용하여야 할 것이다.

• 한국항공우주학회지
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• 제35권9호
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• pp.753-760
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• 2007

3-D 날개짓 운동은 왕복운동과 회전운동으로 구성된다. 3-D 날개짓 운동은 왕복운동하는 동안 날개 길이방향의 유동이 발생된다. 또한 각각의 왕복운동의 끝에서 날개 회전에 의하여 회전에 의한 순환이 발생한다. 본 연구에서는 날개 길이방향 유동과 날개 회전이 3-D 날개짓 운동의 공기역학적 특성에 미치는 영향을 알아보기 위하여 3-D 날개짓 운동과 2-D 병진운동을 비교하였다. 각각의 날개짓 운동에서 받음각과 레이놀즈수에 따라 공력을 측정하였다. 2-D 병진운동의 공력이 3-D 날개짓 운동의 공력 보다 크다. 하지만 3-D 날개짓 운동시 발생되는 양력은 왕복운동의 중반부에서 받음각 $50^{\circ}$까지 증가하였고 2-D 병진운동시 발생되는 양력은 받음각 $30^{\circ}$이상에서 감소하였다. 또한 각각의 왕복운동의 끝에서 날개 회전에 의하여 공력이 급격하게 증가하였다.