Published October 22, 1979 | Version v1
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Contribution to the study of turbulence in the liquid phase of bubbles flows

Creators

Description

The present work aims at overcoming the insufficiency of information related to two-phase water-air bubble flows which have the double advantage of being 'simple' and of having an industrial interest. The aim is to provide a detailed experimental description of a uniform co-current, vertical ascending flow, as complete as that commonly encountered for single-phase flows. It is examined how the injection of bubbles affects the turbulence of a uniform turbulent flow generated by a grid in a channel. The quantities to be measured in priority have been suggested by a theoretical analysis of the fundamental equations of turbulence in two-phase flows. Chapter II is devoted to a detailed bibliographic analysis of the very limited set of articles dealing with this problem. In Chapter III, it is established, from the two-phase flow equations, the set of equations governing for each phase the evolution of classical turbulent quantities: velocity, pressure, Reynolds tensor, dissipation. In addition to terms similar to those encountered in monophasic turbulence, they contain terms of interfacial transfers, which must be estimated and measured if one wants to be able to proceed to the numerical treatment of such flows. In Chapter IV, the envisaged experiment is defined, the installation and the metrological means used are described. Moreover, the results of the qualification tests of the hydrodynamic tunnel with or without the grid, are provided and discussed in the monophasic case. Chapter V is devoted to discussing the methods of signal processing adopted for different quantities. Finally, in Chapter VI, all the preliminary results obtained are given (turbulent intensity, coefficients of dissymmetry and flattening, as a function of the void rate and the average velocity of the liquid, influence of the diameter of the injectors and spectra). and an interpretation is provided (still imperfect) of a complete and reliable image of the whole flow. One of the most striking results obtained is the demonstration of two rather distinct differential flow regimes: the first one is observed at low speed, whatever the void ratio, and seems to correspond to a turbulence due to bubble agitation, while the second one is characterized by a turbulent intensity that is independent of the speed and is reminiscent of the situation encountered in single-phase flows

Abstract (French)

Le present travail a ete defini en liaison etroite avec le Departement des Transferts Thermiques du C.E.N.G. et vise a pallier l'insuffisance des informations relatives aux ecoulements diphasiques eau-air a bulles qui ont le double avantage d'etre 'simples' et d'avoir un interet industriel. Le but poursuivi est de fournir une description experimentale detaillee d'un ecoulement uniforme co-courant, vertical ascendant, aussi complete que celles que l'on rencontre couramment pour des ecoulements monophasiques. Il s'agit d'examiner avec precision comment l'injection d'un reseau de bulles affecte la turbulence d'un ecoulement turbulent uniforme engendre par une grille dans un canal. Les grandeurs a mesurer en priorite ont ete suggerees par une analyse theorique des equations fondamentales de la turbulence en ecoulement diphasique. Le chapitre II est consacre a une analyse bibliographique detaillee de l'ensemble tres restreint d'articles traitant de ce probleme. Dans le chapitre III, nous etablissons, a partir des equations des ecoulements diphasiques, l'ensemble des equations regissant pour chaque phase l'evolution des grandeurs turbulentes classiques: fluctuations de vitesse, de pression, tenseur de Reynolds, dissipation. Outre des termes analogues a ceux rencontres en turbulence monophasique, elles contiennent des termes de transferts interfaciaux, qu'il s'agit d'estimer et de mesurer si l'on veut un jour pouvoir proceder au traitement numerique de tels ecoulements. Dans le chapitre IV, l'experience envisagee est definie, l'installation et les moyens metrologiques utilises sont decrits. Par ailleurs, les resultats des essais de qualification du tunnel hydrodynamique muni ou non de la grille, sont fournis et discutes dans le cas monophasique. Le chapitre V est consacre a la discussion des methodes de traitement du signal adoptees pour les differentes grandeurs. Enfin, dans le chapitre VI, nous donnons l'ensemble des resultats preliminaires obtenus (intensite turbulente, coefficients de dissymetrie et d'aplatissement, en fonction du taux de vide et de la vitesse moyenne du liquide, influence du diametre des injecteurs et spectres) et tentons d'en fournir une interpretation encore imparfaite car nous n'avons pas pu obtenir a temps des informations en nombre suffisant pour etre en possession d'une image complete et fiable de l'ensemble de l'ecoulement. L'un des resultats les plus marquants obtenus est la mise en evidence de deux regimes d'ecoulement assez nettement differencies: le premier observe a basse vitesse, quel que soit le taux de vide, correspond, semble-t-il, a une turbulence d'agitation des bulles, tandis que le deuxieme caracterise par une intensite turbulente, independante de la vitesse n'est pas sans rappeler la situation qu'on rencontre en monophasique

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Additional details

Additional titles

Original title (French)
Contribution a l'etude de la turbulence dans la phase liquide des ecoulements a bulles

Identifiers

URL
http://www.iaea.org/inis/Contacts/;

Publishing Information

Imprint Pagination
157 p.
Report number
FRCEA-TH--9697

INIS

Country of Publication
France
Country of Input or Organization
France
INIS RN
50064686
Subject category
S42: ENGINEERING;
Resource subtype / Literary indicator
Thesis
Descriptors DEI
BUBBLES; ENERGY LOSSES; FLOW MODELS; HEAT TRANSFER; HYDRODYNAMICS; INJECTION; INTERFACES; LIQUID FLOW; MASS TRANSFER; MEASURING INSTRUMENTS; MEASURING METHODS; METROLOGY; PRESSURE MEASUREMENT; REYNOLDS NUMBER; SIZE; THERMAL HYDRAULICS; TURBULENCE; TURBULENT FLOW; TWO-PHASE FLOW; VELOCITY
Descriptors DEC
DIMENSIONLESS NUMBERS; ENERGY TRANSFER; FLUID FLOW; FLUID MECHANICS; HYDRAULICS; INTAKE; LOSSES; MATHEMATICAL MODELS; MECHANICS

Optional Information

Notes
24 refs.; Available from the INIS Liaison Officer for France, see the 'INIS contacts' section of the INIS-NKM website for current contact and E-mail addresses: http://www.iaea.org/inis/Contacts/; Also available from Bibliotheque Michel Serres, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France)