• Nuclear Engineering and Technology
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• 제16권2호
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• pp.47-57
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• 1984

2상유동을 해석하기 위한 3차원 코드인 THERMIT-6S의 미분 방정식을 세우기 위해, 수학적으로 정확하게 유도된 시간과 공간에 대해 평균한 보존 방정식을 단순화했다. 미분 방정식을 불연속화(discretization)하여 THERMIT-6S의 차분방정식을 얻는다. First-order spatial scheme, donor cell method, 그리고, staggered mesh layout을 써서 공간에 대한 불연속화를 한다. 그리고 시간에 대한 불연속화는 first-order semi-implicit scheme으로써, sonic terms와 국부적인 전달 현상에 관계되는 항들은 implicit하게 그리고 대류 전달 항들은 explicit하게 취급한다. 이렇게 얻어진 방정식들은Newton-Raphson 방법으로 선형화된다. 축소된 압력 방정식을 만들기 위해 모든 변수들이 mesh cells사이에서 단지 압력 변수를 통해서만 결부되도록, 선형화된 방정식들을 처리한다. OPERA-15 실험을 수치해석적으로 모의실험하여 본 결과, THERMIT-6S가 flow coastdown, 역류, 유체진동(flow oscillation) 등을 포함하고, sodium boiling 후의 원자로내의 변화를 예측하는데 매우 유효하다는 것이 밝혀졌다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.192-197
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• 2003

Three-dimensional cavity flow is analyzed with the code by using unstructured grid. Incompressible Navier-Stokes equations are used as governing equations, and governing equations are discretized by Finite Volume Method. Artificial compressibility method, proposed by Chorin, and developed by Soh, is used for coupling a pressure and a velocity. Cell-centered scheme is adopted in the code, this has the effect of having denser grid than nodal scheme when the same grid is used. Weighted Averaging scheme is used for the value at a nodal point. Cavity flow is analyzed, and this computed results are compared with the results in the research report

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.565-567
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• 2008

In the present study, a least square/level set based two-phase flow code has been developed using finite element discretization, which can be utilized for the analysis of a free surface flow problem in a complex geometry. Since the finite element method is employed for the spatial discretization of governing equations, an unstructured mesh can be naturally adopted for the level set simulation of a bubble-in-liquid flow without an additional load for the code development except that solution methods of the hyperbolic type redistancing and advection equations of the level set function should be devised in order to give a bounded solution on the unstructured mesh. For the discretization of hyperbolic type redistancing and advection equations, least square method is adopted. From the numerical experiments of the present study, it is shown that the proposed method is both robust and accurate.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(2)
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• pp.433-438
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• 1997

It Is necessary to calculate radwaste effluent due to change in the fuel defect rate to see the overall change in radwaste effluent md, at present, for this type of calculation DAMSAM code is being used. However, often, one can not access easily to this code with many reason and so we have chosen this case, in this paper, to show a very simplified but quite accurated calculation method without the solving equations. The physical meanning of the parameters in the equations used in DAMSAM have been reviewed to simplify the equations and the result calculated with this method have been compared with that of DAMSAM.

• International Journal of Aeronautical and Space Sciences
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• 제7권2호
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• pp.155-174
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• 2006

Parabolized stability equations for compressible flows in general curvilinear coordinate system are derived to deal with a broad range of transition prediction problems on complex geometry. A highly accurate finite difference PSE code has been developed using an implicit marching procedure. Compressible and incompressible flat plate flow stability under two-dimensional and three¬dimensional disturbances has been investigated to test the present code. Results of the present computation are found to be in good agreement with the multiple scale analysis and DNS data. Stability calculation results by the present PSE code for compressible boundary layer at Mach numbers ranging from 0.02 to 1.5 are also presented and are again seen to be as accurate as the spectral method.

• 대한기계학회논문집A
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• 제27권3호
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• pp.409-415
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• 2003

The purpose of this paper is to develop the 2-Dim Lagrangian Hydrocode for the analysis of large deformations of solids with implementation of the contact algorithm. First, th e governing equations are discretized into a system of algebraic equations. For more accurate and robust contact force computation. the defense node contact algorithm was adopted and implemented. For the verification of the code developed, two cases are carried out; the Taylor-Impact test and two bodies impact. The von -Mises criterion is implemented into the code with the Shock equation of state. The simulation results show a good agreement compared with the published experimental data and results from the commercial code. It is necessary to implement several material models and failure models for applications to different impact and penetration problems.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall
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• pp.170-177
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• 1999

The natural period calculation equations specified in the current building code are empirical formulas that depend on height and material type of the structure. Building with the upper wall and lower frame type is a unique structure which composed of two different structural system This type of structure needs either the deep transfer girder or the thick transfer plate that brings the sudden change of stiffness and mass. Therefore the natural period equations recommended by the current code can not be applied directly. In this study the natural period of building with typical plan obtained by dynamci analysis is compared with that of various codes. Ad approximate estimation equation for the natural period of building with the upper wall and lower frame type obtained by regression analysis is recommended. by the current code can not be applied directly. In this study the natural period of building with typical plan obtained by dynamic analysis is compared with that of various codes, And approximate estimation equation for the natural period of building with the upper wall and lower frame type obtained by regression analysis is recommended.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.636-655
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• 2010

A thermal-hydraulic code, named CUPID, has been being developed for the realistic analysis of transient two-phase flows in nuclear reactor components. The CUPID code development was motivated from very practical needs, including the analyses of a downcomer boiling, a two-phase flow mixing in a pool, and a two-phase flow in a direct vessel injection system. The CUPID code adopts a two-fluid, three-field model for two-phase flows, and the governing equations are solved over unstructured grids with a semi-implicit two-step method. This paper presents an overview of the CUPID code development and assessment strategy. It also presents the code couplings with a system code, MARS, and, a three-dimensional reactor kinetics code, MASTER.

• 한국전산유체공학회지
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• 제16권2호
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• pp.30-48
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• 2011

A three-dimensional thermal-hydraulic code, CUPID, has been developed for the analysis of transient two-phase flows at component scale. The CUPID code adopts a two-fluid three-field model for two-phase flows. A semi-implicit two-step numerical method was developed to obtain numerical solutions on unstructured grids. This paper presents an overview of the CUPID code development and assessment strategy. The governing equations, physical models, numerical methods and their improvements, and the systematic verification and validation processes are discussed. The code couplings with a system code, MARS, and, a three-dimensional reactor kinetics code, MASTER, are also presented.

• 한국항공우주학회지
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• 제39권9호
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• pp.805-815
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• 2011

비선형 포물형 안정성 방정식(Nonlinear Parabolized Stability Equations, NPSE)은 보다 전체적인 천이 과정 연구에 효과적으로 사용될 수 있다. NPSE는 천이 과정에서 비선형 구간의 안정성을 직접 수치 모사(Direct Numerical Simulation, DNS)에 비해 적은 계산 비용을 사용하여 효율적으로 해석 할 수 있다. 본 연구에서는 일반 좌표계에서의 NPSE를 구성하고, 수치 계산을 위한 코드를 개발하였다. 코드의 검증을 위해 비압축성 및 압축성 평판 경계층에서의 벤치마크 문제들을 해석하였다. 본 연구의 NSPE 해석 기법이 비선형 안정성 연구에 효율적이고 효과적인 방법임을 확인하였다.