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2011
NURESIM AND NURISP EUROPEAN TWO-PHASE CFD RESEARCH
vii-viii
10.1615/MultScienTechn.v23.i2-4.10
D.
Bestion
CEA-Grenoble/ DEN-DM2S-LTMF-LMES, 17 rue des Martyrs, 38054 Grenoble, France
TWO-PHASE CFD: THE VARIOUS APPROACHES AND THEIR APPLICABILITY TO EACH FLOW REGIME
101-128
10.1615/MultScienTechn.v23.i2-4.20
D.
Bestion
CEA-Grenoble/ DEN-DM2S-LTMF-LMES, 17 rue des Martyrs, 38054 Grenoble, France
Pierre
Coste
Univ Grenoble Alpes, CEA, LITEN, DTCH, LCST,
F-38000 Grenoble, France
Bojan
Niceno
Laboratory for Scientific Computing and Modelling, Paul Scherrer Institut, Villigen-PSI, 5232, Switzerland
Stephane
Mimouni
Electricite de France, R&D Division, MFEE, 6 Quai Watier, 78400 Chatou, France
D.
Lakehal
ASCOMP GmbH, Technoparkstrasse 1, CH-8005 Zurich, Switzerland
Yann
Bartosiewicz
Universite catholique de Louvain (UCLouvain), Institute of Mechanics, Materials, and Civil
engineering (iMMC), Louvain-la-Neuve, Belgium, B-1348.
CFD
two-phase flow
modeling
direct numerical simulation
large eddy simulation
interface
bubbly flow
free surface flow
Two-phase Computational Fluid Dynamics (CFD) or CMFD (Computational Multi-Fluid Dynamics) is being applied to some nuclear reactor thermalhydraulic investigations. The NURESIM and NURISP projects of the European 5th and 6th Framework programs made some pioneering efforts to start some applications to a few selected reactor issues such as the Critical Heat Flux or the Pressurized Thermal shock. The extreme variety of flow configurations in steam-water two-phase flow makes the modeling issue very complex. Myriads of model options are available in the vast domain of CMFD, with various treatments of turbulence and of interfaces; the methods for choosing model options depending on the application have to be clarified. The purpose of this paper is to list and classify model options, to discuss some conditions and limits of applicability of the various options, and to identify the modeling needs for closure of the system of equations. The proposed classification of the modeling approaches is based on the space and time filtering or averaging of basic equations and on the number of phases and fields that are distinguished. The various Flow processes that must be modeled by closure relations are identified for each type of approach. The applicability of each of these methods to each flow regime is defined and the present degree of maturity of the models is evaluated. Considering only Eulerian approaches used in an open medium, it is shown that five main approaches are considered: the RANS approach, the pseudo-DNS approach, and three types of space-filtered methods. Some of these methods can be applied only to a reduced number of flow regimes. Attention is drawn on the need to specify the model options, to guaranty the consistency between options, and to ensure completeness of closure terms.
CFD MODELING OF ADIABATIC BUBBLY FLOW
129-164
10.1615/MultScienTechn.v23.i2-4.30
Eckhard
Krepper
Christophe
Morel
Commissariat a l'Energie Atomique, DEN/DM2S/STMF/LMSF, 17; rue des Martyrs, 38054, Grenoble, Cedex 9, France
Bojan
Niceno
Laboratory for Scientific Computing and Modelling, Paul Scherrer Institut, Villigen-PSI, 5232, Switzerland
Pierre
Ruyer
Institut de Radioprotection et de Surete Nucleaire, CE Cadarache, Bat. 700, BP 3-13 115 Saint Paul lez Durance Cedex, France
computational fluid dynamics
two-phase flow
Euler/Eulerian approach
momentum exchange
bubble-induced turbulence
population balance models
large eddy two-phase flow simulation
This paper describes the simulation of adiabatic gas-liquid flow based on the Eulerian approach. An
adequate characterization of the momentum exchange between the phases is necessary. The basic
experiment investigating the momentum exchange is vertical upward flow in a pipe. This paper
describes the main computational fluid dynamics (CFD) approaches for momentum exchange and
the comparison to experimental results for several test conditions. For large gas-injection rates, a
bubble size distribution including bubble coalescence and fragmentation has to be considered. The
paper describes the concept of the inhomogeneous multiple size group model MUSIG, developed
by ANSYS/CFX and Helmholtz-Zentrum Dresden-Rossendorf (HZDR), which is implemented
in the CFD-code CFX, and a comparable concept of a population balance model implemented in
NEPTUNE CFD [Commissariat a l'Energie Atomique (CEA), Électricit é de France (EDF), Institut
de Radioprotection et de S ûret é Nucl éaire (IRSN) and AREVA]. Measurements performed at HZDR
are used for model validation. Crucial for the quality of the models described are the base approaches
for bubble coalescence and fragmentation. Among other influences, these phenomena depend on the
level of liquid turbulence. Therefore special attention was devoted to CFD simulation of bubbly
turbulent flow based on different model concepts. Concepts based on Reynolds-averaged turbulence
models are described. At the Paul Scherrer Institute, large eddy based studies were performed and
compared to DEDALE experiments. The work was performed within the NURESIM and NURISP
projects under the 6th and 7th European Framework Program.
COMPUTATIONAL FLUID DYNAMICS MODELING OF BOILING BUBBLY FLOW FOR DEPARTURE FROM NUCLEATE BOILING INVESTIGATIONS
165-222
10.1615/MultScienTechn.v23.i2-4.40
Bostjan
Koncar
Josef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Christophe
Morel
Commissariat a l'Energie Atomique, DEN/DM2S/STMF/LMSF, 17; rue des Martyrs, 38054, Grenoble, Cedex 9, France
Stephane
Mimouni
Electricite de France, R&D Division, MFEE, 6 Quai Watier, 78400 Chatou, France
L.
Vyskocil
Department of Thermal-hydraulic Analyses, Nuclear Research Institute Rez plc, 25068 Rez, Czech Republic
M. C.
Galassi
Department of Mechanics, Nuclear and Production Engineering-DIMNP, Universita di Pisa, 2, Via Diotisalvi, 56100 PISA, Italy
boiling bubbly flow
CFD
DNB
fuel rod bundle
Predictions of local boiling flow processes leading to departure from nucleate boiling (DNB) conditions are considered. The work was performed within the Nuclear Reactor Simulations project (NURESIM) within the Sixth European Framework program. This paper focuses on the Reynolds-averaged Navier-Stokes (RANS) approach as being the most reliable for simulation of realistic bubbly flows. New physical models developed within the NURESIM project are presented and tested on various single-channel boiling experiments, differing in geometry, working fluid, and operating conditions. The applicability of the model for boiling in fuel rod bundles under industrial conditions has been demonstrated.
CFD MODELING OF BOILING ANNULAR-MIST FLOW FOR DRYOUT INVESTIGATIONS
223-251
10.1615/MultScienTechn.v23.i2-4.50
Henryk
Anglart
Nuclear Reactor Technology Division, Physics Department, School of Engineering Sciences,
KTH Royal Institute of Technology,
SE-100 44, Stockholm, Sweden
D.
Caraghiaur
Nuclear Reactor Technology Division, Department of Physics, Royal Institute of Technology, Roslagstullsbacken 21, SE 106 91, Stockholm, Sweden
liquid film
deposition
entrainment
droplet dynamics
This paper presents applications of computational fluid dynamics (CFD) to modeling of two-phase annular-mist flows with evaporating liquid films. This type of two-phase flow exists in boiling channels prior to the onset of dryout. Annular-mist flows have a very complex structure since they contain liquid and vapor, both as the continuous and the dispersed phase. Due to this feature, both the Eulerian-Eulerian as well as the Eulerian-Lagrangian approaches are often used to model such flows. The two approaches, with pertinent conservation equations and closure relationships, are reviewed in this paper.
CFD MODELING OF FREE SURFACE FLOW WITH AND WITHOUT CONDENSATION
253-342
10.1615/MultScienTechn.v23.i2-4.60
Dirk
Lucas
Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics,
Bautzner Landstraße 400, 01328 Dresden, Germany
Pierre
Coste
Univ Grenoble Alpes, CEA, LITEN, DTCH, LCST,
F-38000 Grenoble, France
T.
Hohne
Helmholtz-Zentrum Dresden-Rossendorf (HZDR) - Institute of Fluid Dynamics P.O.Box 510119, D-01328 Dresden, Germanyy
D.
Lakehal
ASCOMP GmbH, Technoparkstrasse 1, CH-8005 Zurich, Switzerland
Yann
Bartosiewicz
Universite catholique de Louvain (UCLouvain), Institute of Mechanics, Materials, and Civil
engineering (iMMC), Louvain-la-Neuve, Belgium, B-1348.
separated flow
free surface
CFD
This paper presents some recent developments on CFD models suitable to simulate free surface flows, which so far have represented an unresolved matter for industrial nuclear reactors issues. While the general dynamics of such a large interface should be simulated in a CFD approach, all subgrid scale effects have to be modeled. Depending on choice of the general approach, i.e., one-fluid or multifluid models, different closures are required. The momentum transfer between the phases is usually reflected by a drag model in a two-fluid approach. The drag force depends on the local morphology (free surface or dispersed bubbles/drops) and has to be anisotropic at the free surface. Surface tension has to be considered at wavy surfaces. The situation becomes even more complex if mass transfer occurs at the interface. Three approaches with different detailedness are presented. Examples for CFD simulations for free surface flow using different CFD codes and approaches are discussed.
author index
344
10.1615/MultScienTechn.v23.i2-4.70
subject index
345
10.1615/MultScienTechn.v23.i2-4.80