A model for stratified gas-liquid turbulent flow in ducts of arbitrary cross-section

We propose a theory to calculate the pressure gradient and the liquid fraction in two-phase gas-liquid fully developed stratified flow in a cylindrical duct of arbitrary cross-section and slope and its application to near horizontal ducts. Its validity is limited to Reynolds numbers high enough to ensure turbulent flow in both phases. Droplet entrainment or bubble inclusion have not been taken into account. The comparison between calculations and experimental values obtained with air and water in circular and rectangular ducts is very satisfactory

A model for stratified gas-liquid turbulent flow in ducts of arbitrary cross-section

We propose a theory to calculate the pressure gradient and the liquid fraction in two-phase gas-liquid fully developed stratified flow in a cylindrical duct of arbitrary cross-section and slope and its application to near horizontal ducts. Its validity is limited to Reynolds numbers high enough to ensure turbulent flow in both phases. Droplet entrainment or bubble inclusion have not been taken into account. The comparison between calculations and experimental values obtained with air and water in circular and rectangular ducts is very satisfactory.Nous proposons une théorie permettant le calcul du gradient de pression et du taux de liquide d'un écoulement diphasique gaz-liquide établi en configuration stratifiée dans une conduite cylindrique de section et d'inclinaison quelconques et son application à une conduite faiblement inclinée sur l'horizontale. La validité est limitée aux valeurs des nombres de Reynolds pour lesquels l'écoulement est turbulent dans les deux phases. L'entraînement de gouttelettes dans la phase gazeuse ou de bulles dans la phase liquide n'est pas pris en compte. La comparaison du calcul et de valeurs expérimentales obtenues avec l'air et l'eau dans des conduites circulaires et rectangulaires est très satisfaisante

Bilans hydrique et énergétique sur une zone urbaine hétérogène: mesures et simulations

National audienc

Numerical investigation of bend and torus flows—Part II : Flow simulation in torus reactor

International audienceFlow in a torus reactor with straight parts fitted with a marine impeller is investigated. The laser Doppler anemometry (LDA) is first employed to achieve experimental measurements of mean velocity profiles. Next, a numerical resolution of the steady-state flow is performed using a multiple reference frames (MRF) approach to represent the particular flow induced by the marine impeller in the geometry. A comparison of predictions using different turbulence models to LDA measurements is made, and a k–ω model is assessed.The numerical tool is used to investigate in more details the particular ow induced in the torus geometry. Evolution of the axial and rotating motions when moving away from the impeller is especially investigated, showing the complex hydrodynamical interaction between the main rotating swirl motion involved downstream the impeller, and bend curvature e ects. Two di erent ow conditions can be considered in the torus geometry, with a main swirling motion close to the impeller, which freely decays and vanishes when Dean vortices appear in bends. Simulations for two rotation velocities of the impeller and comparison with the study with simple bends (ÿrst part) reveal pertinence of the swirl number Sn to describe the change of ow conditions along the reactor axis. When this parameter decreases below a threshold value around 0.2 in a bend entry, centrifugal e ects due to bend curvature are more important than the swirl motion, and Dean vortices appear in bend outlet. One main consequence is the axial distance of the swirl motion persistence, which is found to be smaller for the higher impeller rotation velocity, due to the dual e ect of the marine impeller that generates simultaneously both axial and rotating motions

La campagne expérimentale FluxSAP 2010; mesures de climatologie en zone urbaine hétérogène

National audienc

Suivi expérimental hydrologique et énergétique d'un petit bassin versant urbain

Colloque avec actes et comité de lecture. International.International audienc

Numerical and experimental tracer dispersion study for footprint assessment

International audienc

Vertical and horizontal concentration profiles from a tracer experiment in a heterogeneous urban area

International audienc

Radiative and heat storage properties of the urban fabric derived from analysis of surface forms

International audienc

Aerosol dry deposition in the urban environment: Assessment of deposition velocity on building facades.

International audienc