Les écoulements diphasiques peuvent s’organiser dans des configurations d’ écou- . pour l’amortissement diphasique dans les écoulements `a bulles et. Dans ce mémoire, on s’intéresse à la simulation des écoulements liquide-vapeur en transition de phase. Pour décrire ces écoulements, une approche bifluide. lumes Finis des écoulements diphasiques eau-vapeur. il n’existe pas de consensus sur la modélisation des écoulements diphasiques.

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Structure and kinematics of bubble flow; Structure et cinematique des ecoulements diphasiques a bulles. Centre d’ Etudes Nucleaires.

This report deals with the components and use of resistivity probes in bubble flow. With a single probe, we have studied the longitudinal and radial structure of the flow. The very complicated evolution of the radial structure is shown by the measurement of the mean bubble flux at several points in the tube.

A double probe associated with a device the principle of which is given in this report, permits the measure of the local velocity of bubbles. Unlike the mean bubble flux profile, the change in the velocity profile along the tube is not significant.

We have achieved the synthesis of these two pieces of information, mean local bubble flux and local velocity, by computing the mean weighed velocity in the tube. This weighed velocity compares remarkably with the velocity computed from the volumetric gas flow rate and the mean void fraction.

Les fluides sont l’air et l’eau, ils circulent du bas vers le haut dans un tube vertical de 32 mm de diametre et 2 metres de long. Cette etude a pour but de permettre une description fine de l’ ecoulement. Pour cela, il a ete necessaire de developper des appareillages nouveaux et de mettre au point les methodes d’analyses correspondantes. La valeur des mesures effectuees et des methodes utilisees apparait dans une comparaison concluante et conclusive entre des resultats de mesures globales et des resultats integres de mesures locales.

Structure of two-phase air-water flows. Study of average void fraction and flow patterns; Structure des ecoulements diphasiques eau-air. Etude de la fraction de vide moyenne et des configurations d’ ecoulement.

This report deals with experimental work on a two phase air-water mixture in vertical tubes of different diameters. The average void fraction was measured in a 2 metre long test section by means of quick-closing valves. Using resistive probes and photographic techniques, we have determined the flow patterns and developed diagrams to indicate the boundaries between the various patterns: In the case of bubble flow and slug flow, it is shown that the relationship between the average void fraction and the superficial velocities of the phases is given by: Nous avons mesure la fraction de vide moyenne dans une portion de canal de longueur 2 m, au moyen d’un systeme de vannes a fermeture rapide et simultanee.

Au moyen de sondes resistives et de photographies nous avons determine la configuration de l’ ecoulement et trace des cartes donnant les frontieres entre les differentes configurations d’ ecoulement: Pour les regimes semi-annulaire et annulaire, il semble qu’en premiere approximation, la fraction de vide moyenne ne depende que. Measurement of the local void fraction in two-phase air-water flow with a hot-film anemometer; Mesure du taux de vide local en ecoulement diphasique eau-air par un anemometre a film chaud.

The experimental knowledge of the local void-fraction is basic for the derivation of the constitutive equations of two-phase flows. This report deals with measurements of the local void-fraction based on the use of a constant temperature hot-film anemometer associated with a multichannel analyser.

After determining the void-fraction profile along a diameter of a vertical pipe 40 mm I. Two runs were made in bubble flow and a third in slug flow. The two methods give results in a good agreement especially for bubble flow.

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The void-fraction averaged over the cross-section was also calculated from the different profiles and ecoulementz in a good manner with the experimental results of R.

For bubble flow we verified the theory of S. Les essais ont ete faits en ecoulements a ecoulemehts et a bouchons. Les deux methodes donnent des resultats concordants ecpulements particulier pour les ecoulements a bulles. Le taux de vide moyenne dans la section, calcule a partir des differents profils, a egalement ete compare avec succes aux resultats experimentaux de R. Dans l’etude de la structure radiale des ecoulements a bulles, nous avons verifie l’hypothese de S.

Fundamental equations for two-phase flow. As a result a detailed study has been made of ecoulemenrs work of C. ZUBER; a summary of this work presented. Ces equations sont presentees sous plusieurs formes a partir des equations integrales qui sont posees dihasiques priori. Equations aux variables locales instantanees et conditions d’interface; 2.

Equations aux variables instantanees moyennees dans une section et applications pratiques: Equations aux moyennes statistiques locales et equations moyennees dans le temps: On obtient alors des equations ou interviennent des variables moyennees dans le temps par application d’une hypothese ergodique. Combinaisons des moyennes statistiques et des moyennes dans une section: Equations generales relatives aux emulsions: Cette particularite permet de definir une concentration volumique locale et d’etablir des equations aux applications multiples.

Ecoulement a complete et precise certains points de la premiere partie de ce rapport concernant les equations generales de conservation des ecoulements diphasiques. On a introduit dans les equations generales les termes correspondant a la tension interfaciale. On a introduit dans les equations generales les termes correspondant a la tension. Directory of Open Access Journals Sweden. Two-phase gas-liquid flows were analyzed ecoulemetns as to develop models for prediction of pressure drops in crude-oil production lines.

The experiments were performed on the two-phase loop at Boussens under the following representative industrial conditions: The pressure gradient, average content and local phase distribution were measured. Conservation phase equations integrated along the cross-section were processed by ecouleemnts time-averaged operators so as to develop a cellular model including a limited number of constitutive equations required for its closure. This model suitably predetermines the pressure gradient, the average gas content and the length of gas and liquid slug.

Calculation programme for transient thermo-pneumatic flows; Programme de calcul pour les ecoulements transitoires thermopneumatiques.

With a view to determining the changes occurring in gas reactors after cooling accidents, a calculation programme is established for unidimensional gas flows with pressure drops, heat exchanges and in certain cases eclulements, in a reticulated lattice.

Any schematization can be taken into account by the use of a set of indices. The results obtained are in good agreement with those obtained both from the graphical method using the characteristics and from experimental recorded data. Toute schematisation peut etre prise en compte grace a un jeu d’indices.

Ses resultats sont en bon accord, d’une part avec ceux de la methode graphique des caracteristiques, d’autre part avec des enregistrements experimentaux.

Numerical simulation of two phase flows in heat exchangers; Simulation numerique des ecoulements diphasiques dans les echangeurs. The report presents globally the works done by the author in the thermohydraulic applied to nuclear reactors flows.

It presents the studies done to the numerical simulation of the two phase flows in the steam generators and a finite element method to compute these flows.

Towards Eulerian-Eulerian large eddy simulation of reactive two-phase plows; Vers la simulation des grandes echelles en formulation Euler-Euler des ecoulements reactifs diphasiques.

### les ecoulements diphasiques: Topics by

Particle laden flows occur in industrial applications ranging from droplets in gas turbines to fluidized bed in chemical industry. Prediction of the dispersed phase properties such as concentration and dynamics are crucial for the design of more efficient devices that meet the new pollutant regulations of the European community. Numerical simulation coupling Lagrangian tracking of discrete particles with DNS or LES of the carrier phase provide a well established powerful tool to investigate particle laden flows.

Such numerical methods have the drawback of being numerically very expensive for practical applications. Numerical simulations diphasiquds on separate Eulerian balance equations for both phases, coupled through inter-phase exchange terms might be an effective alternative approach.

This approach has been validated for the case of tracer particles with very low inertia that follow the carrier phase almost instantaneously due to their small response time compared with the micro-scale time scales of the carrier phase.

Objective of this thesis is to extend this approach to more inertial particles that occur in practical applications such as fuel droplets in gas turbine combustors. Existing results suggest a separation of the dispersed phase velocity into a correlated and an uncorrelated component. The presence of this uncorrelated motion leads to stress terms in the Eulerian balance equation for the particle momentum. Models for this stress terms are proposed and tested. Numerical simulations in the Eulerian framework are validated diphwsiques comparison with simulations using Lagrangian particle tracking.

Dcoulements coupling of the Eulerian transport equations for the particles to combustion models is tested. Some numerical methods for two-fluid two-phase flows in oil pipes; Quelques methodes numeriques pour les ecoulements diphasiques bi-fluide en conduites petrolieres. This thesis is devoted to the numerical simulation of some two-fluid models describing gas-liquid two-phase flow in pipes. The numerical models developed here can be more generally used in the modelling of a wide class of physical models which can be put under an hyperbolic form.

We introduce first two isothermal two-fluid models, composed of a mass balance equation and a momentum equation written in each phase, describing respectively viphasiques stratified two-phase flow and a dispersed two-phase flow.

These models are hyperbolic under some physical assumptions and can be written under a nonconservative vectorial system. This scheme does not need any analytical calculation and gives good results in the tracking of shocks.

We compare this new scheme with the classical Roe scheme. Then we propose and study some numerical models, with and without flux splitting method, which are adapted to the discretization of the two-fluid models.

In order to reducing cpu time, due to the low Mach number of two-phase flows, acoustic waves are implicit. Afterwards we proposed a discretization of boundary conditions, which allows the generation of transient flows in pipe. Some numerical academic and more physical tests show the good behaviour of the numerical methods. Up scaling two-phase ecoulemengs in heterogeneous porous media; Mise a l’echelle des ecoulements diphasiques dans les milieux poreux heterogenes.

For two-phase flow in ecohlements media, the emergence of different flow regimes at large-scale is driven by local interactions between the viscous coupling and the heterogeneity. In particular, when the viscosity ratio is favorable, viscous effects induce a transverse flow that stabilizes the front while flooding.

However, ecoulement of recent stochastic models neglect the influence of the viscous coupling. We ecoulemebts a stochastic model for the ecoylements of the front, taking the viscous coupling into account. For stable cases, this model relates the statistical properties of the front to the statistical properties of the permeability field.

For stable flow in stratified media, we show that the front is stationary by parts in the reservoir. These parts can be identified as large-scale hydrodynamic layers and separately coarsened in the large-scale simulation model. For flows with favorable viscosity ratios in isotropic reservoirs, we show that a stationary front occurs, in a statistical sense. For unfavorable viscosity ratios, the flow is driven by the development of viscous fingering.

These different regimes lead to different large-scale saturation profiles that can be matched with a macro-dispersion equation, if the effective convective flux is modified to take into account stabilizing or destabilizing viscous effects.