고전압 방전회로에서 생성된 펄스형 자장의 해석

정운관,우승웅,육종철 조선대학교 원자력연구소 1990 原子力硏究 Vol.4 No.-

Theta pinch is a kind of thermonuclear fusion devices, which produces a strong magnetic field inside a cylindrical plasma container by its high voltage pulse generating circuit system, and improves the density and temperature of plasma by its strong magnetic field. High voltage circuit system consists of a 1㎌ capacitor of charging voltage of 10kV, spark switch, triggering system, and a 36cm long pinch coil of diameter 30cm. The pulsed magnetic field are measured by a magnetic probe at the various position in the pinch coil. The experimental results show that the magnetic field had a period of 4.3㎲ and a maximum value of 560 Gauss at the center of pinch coil, and the spatial variation of magnetic field obtained by the numerical method of computer calculation agree with the experimental results.

Si, PIN 광 다이오드를 이용한 플라즈마 가열구조의 해석

정운관,우승웅,육종철 조선대학교 원자력연구소 1990 原子力硏究 Vol.4 No.-

This study is to investigate the heating mechanism of a produced plasma by theta pinch device. The temperal and spatial dependency of pulse magnetic field is measured by a magnetic probe, which is inserted into three different positions in the plasma tube. The transformation of wavelength in plasma light is measured by a Si-PIN photodiode at the various plasma tube pressures. The experimental results show that the largest plasma current and light signal occurred at the initial pressure of 2.5X10^-2 mmHg and the magnetic field cannot be penetrated into the center of the plasma column.

칼란드리아 내부의 감속재 열유동 해석을 위한 난류 모델 성능 평가

이공희(Gonghee Lee),방영석(Youngseok Bang),우승웅(Swengwoong Woo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

It is experimentally well-known that the thermal flow in the CANDU calandria is generally complex and highly turbulent due to the interaction of buoyancy force with inlet jet inertia. In this study, to assess the prediction performance of turbulence models, the results obtained with the commercial flow solver, FLUENT<SUP>(1)</SUP>, is compared with experimental data for Sheridan Park Engineering Laboratory (SPEL) test vessel<SUP>(2)</SUP>. Through this comparative study of turbulence models, it is concluded that turbulence models including the source term to consider the effects of buoyancy on the turbulent flow should be used to predict reliably the thermal flow inside the CANDU calandria.

칼란드리아 내부의 감속재 열유동 해석을 위한 난류모델 성능 평가

이공희(Gong Hee Lee),방영석(Young Seok Bang),우승웅(Sweng Woong Woo) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.3

CANDU형 원전의 칼란드리아 내부 감속재 열유동은 입구 노즐에서 나온 제트 유동에 의해 발생하는 관성력과 감속재로 전달되는 열부하에 의해 발생하는 부력의 상호작용으로 인해 복잡한 난류 특성을 나타낸다. 본 연구에서는 이러한 복잡한 감속재 열유동을 정확히 예측하기 위한 난류모델의 성능을 평가하기 위해 상용 유동해석 프로그램인 FLUENT에 탑재된 난류모델들을 사용해서 계산한 결과를 Sheridan Park Engineering Laboratory (SPEL)의 실험값과 비교하였다. 결론적으로 CANDU형 원전의 칼란드리아 내부 감속재 열유동을 신뢰할 수 있게 예측하기 위해서는 부력이 난류 유동에 미치는 영향을 고려해주는 생성항을 포함한 난류 모델이 사용되어야 한다. The moderator thermal flow in the CANDU calandria is generally complex and highly turbulent because of the interaction of the buoyancy force with the inlet jet inertia. In this study, the prediction performance of turbulence models for the accurate analysis of the moderator thermal flow are assessed by comparing the results calculated with various types of turbulence models in the commercial flow solver FLUENT with experimental data for the test vessel at Sheridan Park Engineering Laboratory (SPEL).Through this comparative study of turbulence models, it is concluded that turbulence models that include the source term to consider the effects of buoyancy on the turbulent flow should be used for the reliable prediction of the moderator thermal flow inside the CANDU calandria.

환형관내 농도 소스에 의한 난류 스칼라 확산의 수치해석

윤동혁(Dong-Hyeog Yoon),정애주(Ae-Ju Cheong),방영석(Young Seok Bang),우승웅(Sweong Woong Woo) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.5-2

원자로 내부 구조물 형상 처리 방법이 축소 APR+ 유동분포 예측 정확도에 미치는 영향에 관한 수치적 연구

이공희(Gong Hee Lee),방영석(Young Seok Bang),우승웅(Sweng Woong Woo),정애주(Ae Ju Cheong) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.3

원자로 노심 입구에 위치한 내부 구조물들은 형상 및 노심 입구까지의 상대적 거리에 따라 노심 입구유량분포에 상당한 영향을 미칠 수 있다. 본 연구에서는 원자로 내부 구조물 형상 처리 방법이 축소 APR+ 유동분포 예측 정확도에 미치는 영향을 조사하기 위해 상용 전산유체역학 소프트웨어인 ANSYS CFX R.14를 사용하여 원자로 내부 구조물들의 실제 형상을 고려한 계산을 수행하였고 다공성 매질 가정을 적용한 계산 결과와 비교하였다. 결론적으로 노심 입구 상류에 위치한 원자로 내부 구조물의 실제 형상을 고려함으로써 노심 입구 유량 분포를 더 정확하게 예측할 수 있었다. 따라서 충분한 계산 자원이 확보된 조건인 경우라면 정확한 노심 입구 유량분포를 계산하기 위해 노심 입구 상류에 위치한 원자로 내부 구조물들(예: 하부지지구조물 바닥판 및 노내 계측기 노즐 지지판)의 실제 형상을 고려해서 계산하는 것이 필요하다. Internal structures, especially those located in the upstream of a reactor core, may have a significant influence on the core inlet flow rate distribution depending on both their shapes and the relative distance between the internal structures and the core inlet. In this study, to examine the effect of the reactor internal structure geometry treatment method on the prediction accuracy for the scale-down APR+ flow distribution, simulations with real geometry modeling were conducted using ANSYS CFX R.14, a commercial computational fluid dynamics software, and the predicted results were compared with those of the porous medium assumption. It was concluded that the core inlet flow distribution could be predicted more accurately by considering the real geometry of the internal structures located in the upstream of the core inlet. Therefore, if sufficient computational resources are available, an exact representation of these internal structures, for example, lower support structure bottom plate and ICI nozzle support plate, is needed for the accurate simulation of the reactor internal flow.

원자로 내부유동 예측을 위한 상용 전산유체역학 소프트웨어 성능 비교 연구

이공희(Gong Hee Lee),방영석(Young Seok Bang),우승웅(Sweng Woong Woo),김도형(Do Hyeong Kim),강민구(Min Ku Kang) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.12

전산유체역학 소프트웨어의 일부 개발자 및 사용자는 최신 전산유체역학 소프트웨어가 최소한 단상 원자로 안전문제는 타당하게 해석할 수 있을 것으로 생각하지만 계산 결과에는 여전히 제한성 및 불확실도가 존재한다. 현재 한국원자력안전기술원에서는 규제관점에서 원자로 안전문제에 대한 상용 전산유체역학 소프트웨어의 성능평가를 수행하고 있다. 본 연구에서는 축소 APR+ 원자로 내부유동 해석시 다공성 모델을 적용한 상용 전산유체역학 소프트웨어의 예측 성능을 평가하기 위해 ANSYS CFX R.14 및 FLUENT R.14 에 탑재된 수치모델을 이용하여 계산을 수행하였다. 결론적으로 전산유체역학 소프트웨어에 따라 축소 APR+ 원자로 내부유동 분포는 국부적으로 차이가 발생하였다. 비록 제한된 수의 측정치로 인해 상용 전산유체역학 소프트웨어간 예측성능을 평가하기에는 다소 한계가 있으나 CFX R.14 가 FLUENT R.14 에 비해 상대적으로 타당한 예측결과를 제시하였다. 한편 적용된 차분법의 차이로 인해 동일한 격자에 대해 FLUENT R.14 가 CFX R.14 에 비해 상대적으로 많은 계산 메모리를 필요로 하였다. 따라서 대용량 병렬 계산시 가용한 계산 자원에 적합한 전산유체역학 소프트웨어가 선정되어야 한다. Even if some CFD software developers and its users think that a state-of-the-art CFD software can be used to reasonably solve at least single-phase nuclear reactor safety problems, there remain limitations and uncertainties in the calculation result. From a regulatory perspective, the Korea Institute of Nuclear Safety (KINS) is presently conducting the performance assessment of commercial CFD software for nuclear reactor safety problems. In this study, to examine the prediction performance of commercial CFD software with the porous model in the analysis of the scale-down APR (Advanced Power Reactor Plus) internal flow, a simulation was conducted with the on-board numerical models in ANSYS CFX R.14 and FLUENT R.14. It was concluded that depending on the CFD software, the internal flow distribution of the scale-down APR was locally somewhat different. Although there was a limitation in estimating the prediction performance of the commercial CFD software owing to the limited amount of measured data, CFX R.14 showed more reasonable prediction results in comparison with FLUENT R.14. Meanwhile, owing to the difference in discretization methodology, FLUENT R.14 required more computational memory than CFX R.14 for the same grid system. Therefore, the CFD software suitable to the available computational resource should be selected for massively parallel computations.

유동 덮개 형상이 축소 APR+ 내부 유동분포에 미치는 영향에 대한 수치해석

이공희(Gong Hee Lee),방영석(Young Seok Bang),우승웅(Sweng Woong Woo),김도형(Do Hyeong Kim),강민구(Min Ku Kang) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.5

In this study, in order to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ (Advanced Power Reactor Plus) internal flow, simulation was conducted with the commercial multi-purpose computational fluid dynamics software, ANSYS CFX V.14. In addition, among the various reactor internals, the effect of flow skirt geometry on reactor internal flow was investigated. It was concluded that the porous model for some reactor internal structures could adequately predict the hydraulic characteristics inside the reactor in a qualitative manner. If sufficient computation resource is available, the predicted core inlet flow distribution is expected to be more accurate, by considering the real geometry of the internal structures, especially located in the upstream of the core inlet. Finally, depending on the shape of the flow skirt, the flow distribution was somewhat different locally. The standard deviation of the mass flow rate(σ) for the original shape of flow skirt was smaller, than that for the modified shape of flow skirt. This means that the original shape of the flow skirt may give a more uniform distribution of mass flow rate at the core inlet plane, which may be more desirable for the core cooling.

CFD 우수사례 지침을 적용한 관 다발 주위의 난류유동 수치해석

이공희(Gong Hee Lee),방영석(Young Seok Bang),우승웅(Sweng Woong Woo),정애주(Ae Ju Cheng) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.10

본 연구에서는 상용 전산유체역학 소프트웨어인 ANSYS CFX V.13을 사용하여 정상상태, 비압축성, 등온으로 가정된 엇갈림 관 다발 및 일렬 관 다발 주위의 난류유동을 계산하였다. 계산 결과는 전산유체역학 우수사례 지침에 근거하여 격자크기, 대류항 차분법의 정확도 및 난류모델에 대한 민감도 연구에 활용되었고 실험 결과와 정량적으로 비교함으로써 우수사례 지침의 적용성을 평가하였다. 결론적으로 전산유체역학 우수사례 지침이 관 다발 유동 분야에서 상용 전산유체역학 소프트웨어의 예측성능 향상을 반드시 보증하지 않음을 확인하였다. In this study, the numerical analysis of a turbulent flow around both a staggered and an inline tube bundle was conducted using ANSYS CFX V.13, a commercial CFD software. The flow was assumed to be steady, incompressible, and isothermal. According to the CFD Best Practice Guideline, the sensitivity study for grid size, accuracy of the discretization scheme for convection term, and turbulence model was conducted, and its result was compared with the experimental data to estimate the applicability of the CFD Best Practice Guideline. It was concluded that the CFD Best Practice Guideline did not always guarantee an improvement in the prediction performance of the commercial CFD software in the field of tube bundle flow.

원자로 내부구조물 형상 처리 방법이 축소 APR+ 유동분포 예측 정확도에 미치는 영향에 관한 연구

이공희(Gong Hee Lee),방영석(Young Seok Bang),정애주(Ae Ju Cheong),우승웅(Woong Woo) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

The internal structures, especially located in the upstream of reactor core, may have a significant influence on the core inlet flow rate distribution depending on both their shapes and the relative distance between the internal structures and the core inlet. In this study, in order to examine the effect of reactor internal structure geometry treatment method on the prediction accuracy for the scale-down APR+ flow distribution, simulations with real geometry modeling were conducted with the commercial computational fluid dynamics software, ANSYS CFX R.14 and the predicted results were compared with those of the porous medium assumption. It was concluded that core inlet flow distribution could be predicted more accurately by considering the real geometry of the internal structures, located in the upstream of core inlet. Therefore if the sufficient computation resource is available an exact representation of these internal structures, for examples lower support structure bottom plate and ICI nozzle support plate, is needed for the accurate simulation of reactor internal flow.