• Title/Summary/Keyword: Two phase-flows

Search Result 337, Processing Time 0.022 seconds

THE CUPID CODE DEVELOPMENT AND ASSESSMENT STRATEGY

  • Jeong, J.J.;Yoon, H.Y.;Park, I.K.;Cho, H.K.
    • Nuclear Engineering and Technology
    • /
    • v.42 no.6
    • /
    • pp.636-655
    • /
    • 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.

Development of a 3-D CFD Program for Computing Two-Phase Flows with a Level Set Method (Level Set 상경계면 추적법을 적용한 3차원 CFD 프로그램의 개발)

  • Son G.;Hur N.
    • Journal of computational fluids engineering
    • /
    • v.9 no.3
    • /
    • pp.73-80
    • /
    • 2004
  • A LS(Level Set) formulation is developed for computing two-phase flows on non- orthogonal meshes. Compared with the VOF(Volume-of-Fluid) method based on a non-smooth volume-fraction function, the LS method can calculate an interfacial curvature more accurately by using a smooth distance function. Also, it is quite straightforward to implement for 3-D irregular meshes compared with the VOF method requiring much more complicated geometric calculations. The LS formulation is implemented into a general purpose program for 3-D flows and verified through several test problems.

NUMERICAL ANALYSIS OF MULTIPHASE FLOW BY NUFLEX (NUFLEX를 이용한 다상유동의 수치해석)

  • Yu, Tae-Jin;Suh, Young-Ho;Son, Gi-Hun;Hur, Nahm-Keon
    • Journal of computational fluids engineering
    • /
    • v.12 no.2
    • /
    • pp.21-25
    • /
    • 2007
  • A general purpose program NUFLEX has been extended for two-phase flows with topologically complex interface and cavitation flows with liquid-vapor phase change caused by large pressure drop. In analysis of two-phase flow, the phase interfaces are tracked by employing a LS(Level Set) method. Compared with the VOF(Volume-of-Fluid) method based on a non-smooth volume-fraction function, the LS method can calculate an interfacial curvature more accurately by using a smooth distance function. Also, it is quite straightforward to implement for 3-D irregular meshes compared with the VOF method requiring much more complicated geometric calculations. Also, the cavitation process is computed by including the effects of evaporation and condensation for bubble formation and collapse as well as turbulence in flows. The volume-faction and continuity equations are adapted for cavitation models with phase change. The LS and cavitation formulation are implemented into a general purpose program for 3-D flows and verified through several test problems.

Precise Void Fraction Measurement in Two-phase Flows Independent of the Flow Regime Using Gamma-ray Attenuation

  • Nazemi, E.;Feghhi, S.A.H.;Roshani, G.H.;Gholipour Peyvandi, R.;Setayeshi, S.
    • Nuclear Engineering and Technology
    • /
    • v.48 no.1
    • /
    • pp.64-71
    • /
    • 2016
  • Void fraction is an important parameter in the oil industry. This quantity is necessary for volume rate measurement in multiphase flows. In this study, the void fraction percentage was estimated precisely, independent of the flow regime in gas-liquid two-phase flows by using ${\gamma}-ray$ attenuation and a multilayer perceptron neural network. In all previous studies that implemented a multibeam ${\gamma}-ray$ attenuation technique to determine void fraction independent of the flow regime in two-phase flows, three or more detectors were used while in this study just two NaI detectors were used. Using fewer detectors is of advantage in industrial nuclear gauges because of reduced expense and improved simplicity. In this work, an artificial neural network is also implemented to predict the void fraction percentage independent of the flow regime. To do this, a multilayer perceptron neural network is used for developing the artificial neural network model in MATLAB. The required data for training and testing the network in three different regimes (annular, stratified, and bubbly) were obtained using an experimental setup. Using the technique developed in this work, void fraction percentages were predicted with mean relative error of <1.4%.

Numerical Analysis of Cavitation Flow Around Hydrofoils (3차원 수중익형 주위의 캐비테이션 유동 전산해석)

  • Kim, S.H.;Koo, T.K.;Park, W.G.;Kim, D.H.
    • The KSFM Journal of Fluid Machinery
    • /
    • v.11 no.3
    • /
    • pp.7-13
    • /
    • 2008
  • The cavitating flow simulation is of practical importance for many engineering systems, such as pump, turbine, nozzle, Infector, etc. In the present work, a solver for two-phase flows has been developed and applied to simulate the cavitating flows past hydrofoils. The governing equation is the two-phase Navier-Stokes equation, comprised of the continuity equation of liquid and vapor phase. The momentum and energy equation is in the mixture phase. The solver employs an implicit, dual time, preconditioned algorithm using finite difference scheme in curvilinear coordinates. An experimental data and other numerical data were compared with the present results to validate the present solver. It is concluded that the present numerical code has successfully accounted for two-phase Navier-Stokes model of cavitation flow.

Accurate and Robust Computations of Gas-Liquid Two-Phase Flows Part 1: Development of Shock-Stable Two-Phase Schemes (액체-기체 2상 유동장의 정확하고 강건한 해석 Part 1: 충격파 안정적인 2상 유동 수치기법의 개발)

  • Ihm, Seung-Won;Kim, Chong-Am
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.37 no.1
    • /
    • pp.1-16
    • /
    • 2009
  • In this paper, we introduce two-phase versions of RoeM and AUSMPW+ schemes. Both schemes are originally developed for the gas dynamic problems, and have shown superior accuracy, efficiency and robustness. A new shock discontinuity sensing term is derived from the mixture equation of state, which is commonly used in the RoeM and AUSMPW+ schemes for the stable numerical flux calculation. The developed two-phase versions of the schemes are applied to several liquid-gas, large property discrepancy two-phase test problems, including several shock stability test problems. The results show that both schemes maintain the merits exhibited in gas dynamic problems even in two-phase flows.

NEW WALL DRAG AND FORM LOSS MODELS FOR ONE-DIMENSIONAL DISPERSED TWO-PHASE FLOW

  • KIM, BYOUNG JAE;LEE, SEUNG WOOK;KIM, KYUNG DOO
    • Nuclear Engineering and Technology
    • /
    • v.47 no.4
    • /
    • pp.416-423
    • /
    • 2015
  • It had been disputed how to apply wall drag to the dispersed phase in the framework of the conventional two-fluid model for two-phase flows. Recently, Kim et al. [1] introduced the volume-averaged momentum equation based on the equation of a solid/fluid particle motion. They showed theoretically that for dispersed two-phase flows, the overall two-phase pressure drop by wall friction must be apportioned to each phase, in proportion to each phase fraction. In this study, the validity of the proposed wall drag model is demonstrated though one-dimensional (1D) simulations. In addition, it is shown that the existing form loss model incorrectly predicts the motion of the dispersed phase. A new form loss model is proposed to overcome that problem. The newly proposed form loss model is tested in the region covering the lower plenum and the core in a nuclear power plant. As a result, it is shown that the new models can correctly predict the relative velocity of the dispersed phase to the surrounding fluid velocity in the core with spacer grids.

A Comparative Study of Two-phase Heuristic Approaches to General Job Shop Scheduling Problem

  • Sun, Ji Ung
    • Industrial Engineering and Management Systems
    • /
    • v.7 no.2
    • /
    • pp.84-92
    • /
    • 2008
  • Scheduling is one of the most important issues in the planning and operation of production systems. This paper investigates a general job shop scheduling problem with reentrant work flows and sequence dependent setup times. The disjunctive graph representation is used to capture the interactions between machines in job shop. Based on this representation, four two-phase heuristic procedures are proposed to obtain near optimal solutions for this problem. The obtained solutions in the first phase are substantially improved by reversing the direction of some critical disjunctive arcs of the graph in the second phase. A comparative study is conducted to examine the performance of these proposed algorithms.

NUMERICAL METHOD FOR TWO-PHASE FLOW ANALYSIS USING SIMPLE-ALGORITHM ON AN UNSTRUCTURED MESH (비정렬격자 SIMPLE 알고리즘기반 이상유동 수치해석 기법)

  • Kim, Jong-Tae;Park, Ik-Kyu;Cho, Hyung-Kyu;Kim, Kyung Doo;Jeong, Jae-Jun
    • Journal of computational fluids engineering
    • /
    • v.13 no.4
    • /
    • pp.86-95
    • /
    • 2008
  • For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.

WELL-BALANCED ROE-TYPE NUMERICAL SCHEME FOR A MODEL OF TWO-PHASE COMPRESSIBLE FLOWS

  • Thanh, Mai Duc
    • Journal of the Korean Mathematical Society
    • /
    • v.51 no.1
    • /
    • pp.163-187
    • /
    • 2014
  • We present a multi-stage Roe-type numerical scheme for a model of two-phase flows arisen from the modeling of deflagration-to-detonation transition in granular materials. The first stage in the construction of the scheme computes the volume fraction at every time step. The second stage deals with the nonconservative terms in the governing equations which produces states on both side of the contact wave at each node. In the third stage, a Roe matrix for the two-phase is used to apply on the states obtained from the second stage. This scheme is shown to capture stationary waves and preserves the positivity of the volume fractions. Finally, we present numerical tests which all indicate that the proposed scheme can give very good approximations to the exact solution.