• Title/Summary/Keyword: A Transient Two-fluid Three-field Model

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HYDRODYNAMIC SOLVER FOR A TRANSIENT, TWO-FLUID, THREE-FIELD MODEL ON UNSTRUCTURED GRIDS (비정렬격자계에서 과도 이상유동해석을 위한 수치해법)

  • Jeong, J.J.;Yoon, H.Y.;Kim, J.;Park, I.K.;Cho, H.K.
    • Journal of computational fluids engineering
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    • v.12 no.4
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    • pp.44-53
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    • 2007
  • A three-dimensional (3D) unstructured hydrodynamic solver for transient two-phase flows has been developed for a 3D component of a nuclear system code and a component-scale analysis tool. A two-fluid three-field model is used for the two-phase flows. The three fields represent a continuous liquid, an entrained liquid, and a vapour field. An unstructured grid is adopted for realistic simulations of the flows in a complicated geometry. The semi-implicit ICE (Implicit Continuous-fluid Eulerian) numerical scheme has been applied to the unstructured non-staggered grid. This paper presents the numerical method and the preliminary results of the calculations. The results show that the modified numerical scheme is robust and predicts the phase change and the flow transitions due to boiling and flashing very well.

NUMERICAL METHOD FOR THE TWO-FLUID THREE-FIELD MODEL ON AN UNSTRUCTURED MESH (비정렬격자 2-유체 3-상 유동 해석 기법)

  • Kim, J.;Park, I.K.;Cho, H.K.;Yoon, H.Y.;Jeong, J.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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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.

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DEVELOPMENT AND PRELIMINARY ASSESSMENT OF A THREE-DIMENSIONAL THERMAL HYDRAULICS CODE, CUPID

  • Jeong, Jae-Jun;Yoon, Han-Young;Park, Ik-Kyu;Cho, Hyoung-Kyu;Lee, Hee-Dong
    • Nuclear Engineering and Technology
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    • v.42 no.3
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    • pp.279-296
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    • 2010
  • For the analysis of transient two-phase flows in nuclear reactor components, a three-dimensional thermal hydraulics code, named CUPID, has been developed. The CUPID code adopts a two-fluid, three-field model for two-phase flows, and the governing equations were solved over unstructured grids, which are very useful for the analysis of flows in complicated geometries. To obtain numerical solutions, the semi-implicit numerical method for the REALP5 code was modified for an application to unstructured grids, and it has been further improved for enhanced accuracy and fast running. For the verification of the CUPID code, a set of conceptual problems and experiments were simulated. This paper presents the flow model, the numerical solution method, and the results of the preliminary assessment.

THE CUPID CODE DEVELOPMENT AND ASSESSMENT STRATEGY

  • Jeong, J.J.;Yoon, H.Y.;Park, I.K.;Cho, H.K.
    • Nuclear Engineering and Technology
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    • v.42 no.6
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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.

A study on vibration characteristics and tuning of smart cantilevered beams featuring an electo-rheological fulid

  • Park, S.B.;Cheong, C.C.;Suh, M.S.
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.1
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    • pp.134-141
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    • 1993
  • Electro-Rheological(ER) fluids undergo a phase-change when subjected to an external electic field, and this phase-change typically manifests itself as a many-order-of-magnitude change in the rheological behavior. This phenomenon permits the global stiffness and energy- dissipation properties of the beam structures to be tuned in order to synthesize the desired vibration characteristics. This paper reports on a proof-of-concept experimental investigation focussed on evaluation the vibration properties of hollow cantilevered beams filled with an ER fluid. and consequently deriving an empirical model for predicting field-dependent vibration characteristics. A hydrous-based ER fluid consisting of corn starch and silicone oil is employed. The beams are considered to be uniform viscoelastic materials and modelled as a viscously-damped harmonic oscillator. Natural frequency, damping ratio and elastic modulus are evaluated with respect to the electric field and compared among three different beams: two types of different volume fraction of ER fluid and one type of different particle concentration of ER fluid by weight. Transient and forced vibration responses are examined in time domain to demonstrate the validity of the proposed empirical model and to evaluate the feasibility of using the ERfluid as an actuator in a closed-loop control system.

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THE DEVELOPMENT AND ASSESSMENT STRATEGY OF A THERMAL HYDRAULICS COMPONENT ANALYSIS CODE (열수력 기기해석용 CUPID 코드 개발 및 평가 전략)

  • Park, I.K.;Cho, H.K.;Lee, J.R.;Kim, J.;Yoon, H.Y.;Lee, H.D.;Jeong, J.J.
    • Journal of computational fluids engineering
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    • v.16 no.2
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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.

Verification of neutronics and thermal-hydraulic coupled system with pin-by-pin calculation for PWR core

  • Zhigang Li;Junjie Pan;Bangyang Xia;Shenglong Qiang;Wei Lu;Qing Li
    • Nuclear Engineering and Technology
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    • v.55 no.9
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    • pp.3213-3228
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    • 2023
  • As an important part of the digital reactor, the pin-by-pin wise fine coupling calculation is a research hotspot in the field of nuclear engineering in recent years. It provides more precise and realistic simulation results for reactor design, operation and safety evaluation. CORCA-K a nodal code is redeveloped as a robust pin-by-pin wise neutronics and thermal-hydraulic coupled calculation code for pressurized water reactor (PWR) core. The nodal green's function method (NGFM) is used to solve the three-dimensional space-time neutron dynamics equation, and the single-phase single channel model and one-dimensional heat conduction model are used to solve the fluid field and fuel temperature field. The mesh scale of reactor core simulation is raised from the nodal-wise to the pin-wise. It is verified by two benchmarks: NEACRP 3D PWR and PWR MOX/UO2. The results show that: 1) the pin-by-pin wise coupling calculation system has good accuracy and can accurately simulate the key parameters in steady-state and transient coupling conditions, which is in good agreement with the reference results; 2) Compared with the nodal-wise coupling calculation, the pin-by-pin wise coupling calculation improves the fuel peak temperature, the range of power distribution is expanded, and the lower limit is reduced more.

A Numerical Analysis with the FSI Mode on the Characteristics of Flow Field and Discharge Valve Motion in a Rotary Compressor (로터리 압축기의 토출밸브의 미소 거동 및 유동 특성에 대한 FSI(Fluid-Structure Interaction) 기법을 이용한 수치해석)

  • Chae, Hee-Moon;Kim, Chang-Nyung;Park, Sung-Kwan
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.5
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    • pp.112-120
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    • 2008
  • This study has been conducted to investigate the characteristics of flow field and discharge valve motion in a rotary compressor. In this study, a transient three-dimensional numerical analysis using FSI(Fluid-Structure Interaction) model has been employed to analyze the interaction between the discharge valve and the refrigerants in the rotary compressor. It has been observed that two peaks have appeared in the displacement of the discharge valve. The maximum displacement of the discharge valve has been found to be located at the second peak. Also, the input pressure of the refrigerants has been compared with the pressures of the muffler passage and the compressor outlet in the rotary compressor. The pressure has decreased along the pathway in the rotary compressor. And the volume flow rates obtained from the current numerical study have been compared with the experiment at data to verify the validity of the present numerical study. This study may supply the fundamental data for the design of rotary compressors.

A NEW PRESSURE GRADIENT RECONSTRUCTION METHOD FOR A SEMI-IMPLICIT TWO-PHASE FLOW SCHEME ON UNSTRUCTURED MESHES (비정렬 격자 기반의 물-기체 2상 유동해석기법에서의 압력기울기 재구성 방법)

  • Lee, H.D.;Jeong, J.J.;Cho, H.K.;Kwon, O.J.
    • Journal of computational fluids engineering
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    • v.15 no.2
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    • pp.86-94
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    • 2010
  • A thermal-hydraulic code, named CUPID, has been developed for the analysis of transient two-phase flows in nuclear reactor components. A two-fluid three-field model was used for steam-water two-phase flows. To obtain numerical solutions, the finite volume method was applied over unstructured cell-centered meshes. In steam-water two-phase flows, a phase change, i.e., evaporation or condensation, results in a great change in the flow field because of substantial density difference between liquid and vapor phases. Thus, two-phase flows are very sensitive to the local pressure distribution that determines the phase change. This in turn puts emphasis on the accurate evaluation of local pressure gradient. This paper presents a new reconstruction method to evaluate the pressure gradient at cell centers on unstructured meshes. The results of the new scheme for a simple test function, a gravity-driven cavity, and a wall boiling two-phase flow are compared with those of the previous schemes in the CUPID code.

IMPROVEMENT OF A SEMI-IMPLICIT TWO-PHASE FLOW SOLVER ON UNSTRUCTURED MESHES (비정렬 격자계에서의 물-기체 2상 유동해석코드 수치 기법 개선)

  • Lee, H.D.;Jeong, J.J.;Cho, H.K.;Kwon, O.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.380-388
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    • 2010
  • A thermal-hydraulic code, named CUPID, has been developed for the analysis of transient two-phase flows in nuclear reactor components. A two-fluid three-field model was used for steam-water two-phase flows. To obtain numerical solutions, the finite volume method was applied over unstructured cell-centered meshes. In steam-water two-phase flows, a phase change, i.e., evaporation of condensation, results in a great change in the flow field because of substantial density difference between liquid and vapor phases. Thus, two-phase flows are very sensitive to the local pressure that determines the phase change. This in turn puts emphasis on the accurate evaluation of local pressure gradient. This paper presents a new numerical scheme to evaluate the pressure gradient at cell centers on unstructured meshes. The results of the new scheme for a simple test function a gravity-driven cavity, and a wall boiling two-phase flow are compared with those of the previous schemes in the cupid code.

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