A multi-field two-fluid concept for transitions between different scales of interfacial structures

Abstract This paper presents a concept for the CFD-modelling of multiphase flows where both segregated and dispersed flow structures occur simultaneously. Transitions between such morphologies, characterized by different scales of interfacial structures, are investigated and a new multi-field two-fluid strategy for a generalized two-phase flow (GENTOP) is presented. The GENTOP-approach extends the inhomogeneous Multiple Size Group (MUSIG)-model by adding an additional continuous gas phase. Within the MUSIG-framework, mass transfers between different bubble size groups due to coalescence and breakup as well as gas–liquid transfers are described. By modelling an additional mass transfer between the polydispersed and continuous gas phase, transitions between the different gas morphologies can be considered dependent on the flow situation. The continuous gas phase summarizes gas structures which are large enough to be resolved within the computed mesh. Therefore a free surface detection and generalized formulations for interfacial transfer models are introduced. The appearance of one particular gas phase due to mass transfer from another gaseous morphology is demonstrated by means of two demonstration cases: the impingement of a liquid jet on a free surface with an associated entrainment of dispersed bubbles as well as an evolving vertical bubble column showing a wide spectrum of bubble sizes.

[1]  Jean-Marie Seynhaeve,et al.  Modeling free surface flows relevant to a PTS scenario: Comparison between experimental data and three RANS based CFD-codes. Comments on the CFD-experiment integration and best practice guideline , 2010 .

[2]  A. Tomiyama,et al.  Numerical Simulation of Poly-Dispersed Bubbly Flow Using a Multi-Fluid Model , 2007 .

[3]  James H. Duncan,et al.  Air-Entrainment Mechanisms in Plunging Jets and Breaking Waves , 2012 .

[4]  G. Kreiss,et al.  A conservative level set method for two phase flow II , 2005, Journal of Computational Physics.

[5]  A. E. Dukler,et al.  Modelling flow pattern transitions for steady upward gas‐liquid flow in vertical tubes , 1980 .

[6]  Thomas Höhne,et al.  Experimental investigation and CFD simulation of horizontal stratified two-phase flow phenomena , 2008 .

[7]  Maurizio Brocchini,et al.  The dynamics of strong turbulence at free surfaces. Part 1. Description , 2001, Journal of Fluid Mechanics.

[8]  Eckhard Krepper,et al.  A population balance approach considering heat and mass transfer—Experiments and CFD simulations , 2011 .

[9]  Naoki Shimada,et al.  Modeling and Hybrid Simulation of Bubbly Flow , 2006 .

[10]  H. Blanch,et al.  Bubble coalescence and break‐up in air‐sparged bubble columns , 1990 .

[11]  K. Yan,et al.  A coupled model for simulation of the gas–liquid two-phase flow with complex flow patterns , 2010 .

[12]  Graham B. Wallis,et al.  Two-Phase Slug Flow , 1961 .

[13]  Stojan Petelin,et al.  Coupling of the interface tracking and the two-fluid models for the simulation of incompressible two-phase flow , 2001 .

[14]  Assad A. Oberai,et al.  A quantitative sub-grid air entrainment model for bubbly flows , 2009 .

[15]  Deendarlianto,et al.  Numerical simulations of counter-current two-phase flow experiments in a PWR hot leg model using an interfacial area density model , 2011 .

[16]  Paul Galpin,et al.  Coupled Algebraic Multigrid for Free Surface Flow Simulations , 2007 .

[17]  K. Yan,et al.  Hydrodynamic and mass transfer characteristics of slug flow in a vertical pipe with and without dispersed small bubbles , 2011 .

[18]  Hubert Chanson,et al.  Free-surface fluctuations in hydraulic jumps: Experimental observations , 2009 .

[19]  Eckhard Krepper,et al.  The inhomogeneous MUSIG model for the simulation of polydispersed flows , 2008 .

[20]  Eckhard Krepper,et al.  Use of models for lift, wall and turbulent dispersion forces acting on bubbles for poly-disperse flows , 2007 .

[21]  J. Donk.  Water aeration with plunging jets , 1981 .

[22]  Andrea Prosperetti,et al.  On the mechanism of air entrainment by liquid jets at a free surface , 2000, Journal of Fluid Mechanics.

[23]  H. Svendsen,et al.  Theoretical model for drop and bubble breakup in turbulent dispersions , 1996 .

[24]  Lyes Khezzar,et al.  Characterization of plunging liquid jets: A combined experimental and numerical investigation , 2011 .

[25]  Thomas Höhne,et al.  EXPERIMENTS AND NUMERICAL SIMULATIONS OF HORIZONTAL TWO PHASE FLOW REGIMES , 2009 .

[26]  J. Brackbill,et al.  A continuum method for modeling surface tension , 1992 .

[27]  A. K. Biń,et al.  Gas entrainment by plunging liquid jets , 1988 .

[28]  M. Guingo,et al.  Validation of the Large Interface Method of NEPTUNE_CFD 1.0.8 for Pressurized Thermal Shock (PTS) applications , 2012 .

[29]  Djamel Lakehal,et al.  Direct Numerical Simulation of Condensing Stratified Flow , 2008 .

[30]  Borut Mavko,et al.  Simulations of free surface flows with implementation of surface tension and interface sharpening in the two-fluid model , 2009 .

[31]  Eckhard Krepper,et al.  Development of a generalized coalescence and breakup closure for the inhomogeneous MUSIG model , 2011 .

[32]  D. Bestion,et al.  Applicability of two-phase CFD to nuclear reactor thermalhydraulics and elaboration of Best Practice Guidelines , 2012 .