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Papers by Rachid Makhloufi
Strömungssimulation im Wasserbau (Flow Simulation in Hydraulic Engineering), 2006
Schleppspannungsverminderung wurden für verschiedene Temperaturen und Rohrdurchmesser durchgeführ... more Schleppspannungsverminderung wurden für verschiedene Temperaturen und Rohrdurchmesser durchgeführt. Zeitgleich wurden Messungen zur räumlichen Geschwindigkeitsverteilung an der Tensidströmung mit der Hilfe eines PIV-Systems (particle image velocimetry) durchgeführt.
Some additives in solutions (polymers or surfactants, for example) can reduce the friction coeffi... more Some additives in solutions (polymers or surfactants, for example) can reduce the friction coefficient in turbulent flow compared to the water flow (up to 80%). Several parameters such as temperature, concentration and the addition or not of contre-ions were largely studied, but this is not the case of the diameter: this is the subject of this study. The pressure drop and the vortex structures are studied with field measurements obtained by PIV. Mots clefs : reduction de la trainee, additifs, turbulence, frottement.
The pattern formation and stability of a drag reducing fluid in a Taylor-Couette geometry is stud... more The pattern formation and stability of a drag reducing fluid in a Taylor-Couette geometry is studied here by Direct Numerical Simulation. When compared to the Newtonian case, DNS experiments performed on this fluid (shear-thinning with a local shear thickening) show differences in the transition from the Taylor Vortex Flow to the Fully Turbulent Flow : the Wavy Vortex Flow and Modulated Vortices Flow are inhibited and replaced by a disturbed TVF and the Turbulent Taylor Vortex flow presents only two non-circular cells. Furthermore, the larger values of Ref for the drag-reducing fluid, compared to the values of Re in the Newtonian fluid, indicate a delay in the appearance of the turbulence.
Http Www Theses Fr, 1989
Une etude par diffusion elastique et quasi-elastique de la lumiere a ete realisee sur deux sortes... more Une etude par diffusion elastique et quasi-elastique de la lumiere a ete realisee sur deux sortes de dispersions colloidales: des solutions de micelles cylindriques geantes formees a partir de tensioactifs cationiques en presence de sel, et des dispersions de particules metalliques stabilisees par des tensioactifs. Les variations en fonction de la fraction volumique de la phase dispersee et de la temperature, du coefficient de diffusion cooperatif et de l'intensite diffusee, par des solutions aqueuses micellaires de chlorure de cetyltrimethylammonium en presence de chlorure de sodium sont etudiees
Les Cahiers De Rheologie, 1996
Nous montrons les resultats d'un modele microscopique pour les micelles vermiculaires, etudie... more Nous montrons les resultats d'un modele microscopique pour les micelles vermiculaires, etudie par dynamique moleculaire hors equilibre et simule par ordinateur. Le modele 'FENE-C' introduit le processus de cassure-recombinaison dans le modele classique 'multibead spring chain model'. Nous comparons les resultats des simulations avec les predictions des theories mesoscopiques. A l'equilibre, une distribution en exponentielle de la longueur micellaire et une dependance en exponentielle de la longueur moyenne en fonction de l'energie de scission ont ete trouvees. Ces resultats correspondent aux predictions des theories mesoscopiques. L'effet du cisaillement sur la distribution de la taille et sur la longueur moyenne des micelles est reporte et discute. Les anisotropies structurales sous ecoulement sont analysees en terme de facteurs de structure statiques des particules micellaires.
Certaines solutions d'additifs (polymères ou surfactants par exemple) ont le pouvoir de rédui... more Certaines solutions d'additifs (polymères ou surfactants par exemple) ont le pouvoir de réduire le coefficient de frottement en écoulement turbulent comparé à l'écoulement du solvant pur. Dans cette contribution, on abordera l'influence des solutions de CTAC sur la réduction de la traînée en régime turbulent par la mesure des pertes de charge (frottement) et par l'étude de la turbulence (organisation de l'écoulement).
Journal de Physique II, 1997
Physical Review E, 1997
This work reports a rheological study on concentrated solutions of cethyltrimethylammonium chlori... more This work reports a rheological study on concentrated solutions of cethyltrimethylammonium chloride (CTAC) and sodium salicylate (NaSal) at a fixed molar concentration ratio [NaSal]/[CTAC]=0.6. While all the solutions behave as a Maxwell fluid, the measured zero-...
Journal of Non-Newtonian Fluid Mechanics, 2011
Some additives, like surfactants or polymers, in aqueous solutions lead to dramatic drag reducing... more Some additives, like surfactants or polymers, in aqueous solutions lead to dramatic drag reducing effects. Classically the range of concentration of surfactant additive is greater than 500 ppm. It was recently demonstrated that an aqueous solution of CTAC/NaSal (cetyltrimethyl ammonium chloride and sodium salicylate) with a concentration lower than 100 ppm has been found to reduce drag. In this work, the influence of temperature (10-50 • C) and concentration (25-150 ppm) on the drag reduction is studied with an experimental setup. A cross analysis is made from those results. It reinforces the link between the structure of the micelles (rod-like shape) and the drag reduction rate.
Journal of Non-Newtonian Fluid Mechanics, 2007
The aim of this paper is to study by direct numerical simulation the effect of a shear-thickening... more The aim of this paper is to study by direct numerical simulation the effect of a shear-thickening behaviour of a surfactant solution, on the fluid flow, and especially on the friction coefficient in a plane channel flow. A three-dimensional model named Surfactant Drag Reduction ...
Journal of Food Engineering, 2011
IRBM, 2007
The risk of nosocomial infection during surgical operations is one of the main reasons leading to... more The risk of nosocomial infection during surgical operations is one of the main reasons leading to the development of powerful techniques of ventilation within the framework of the operating theatre. During the two last decades, computational fluids dynamics (CFD) have being rapidly expanding. Nowadays it is becoming a tool usually requested to predict the airflow into furnished enclosures. However, CFD
Colloid & Polymer Science, 1999
Building and Environment, 2011
The main parameters which control the emission of volatile organic compounds between wall materia... more The main parameters which control the emission of volatile organic compounds between wall materials and indoor air were examined. A physically based model considers that the global emission phenomenon results from three elementary physical phenomena: diffusion through the boundary layer separating the wall from environment, diffusion within the porous network of the materials, and sorption of the gas molecules on the active sites of the materials. The pollutant transfer between porous material and air is therefore subjected to two complementary resistances and we identify first the resistance which controls the transfer. Then, we predict the global emission time constant from the mass transfer coefficient of convection and the thickness of the material. Experimental results from a small scale chamber are compared to predicted values in the case of acetone emission from chipboard in humid air and for high initial acetone concentration. Good agreement is obtained at the beginning of emission but an acetone retention effect by chipboard is observed, showing that it will be necessary to take into account the interactions of water vapor with materials and the pollutants to achieve accurate modeling of the material VOC emission process.
arer.org
Résumé : Les différents phénomènes physiques élémentaires qui interviennent dans le processus glo... more Résumé : Les différents phénomènes physiques élémentaires qui interviennent dans le processus global de transfert de polluant entre une paroi et l'ambiance (processus d'émission si le polluant est initialement présent dans la paroi ou effet dit de puits s'il est initialement présent dans ...
RÉSUMÉ. Cet article traite d'une étude expérimentale et d'une approche théorique de l&#... more RÉSUMÉ. Cet article traite d'une étude expérimentale et d'une approche théorique de l'influence de l'humidité sur les phénomènes de sorption d'acétone par du bois aggloméré (ce matériau est couramment utilisé, notamment en aménagement intérieur, et son processus de ...
Comptes Rendus Mécanique, 2010
Strömungssimulation im Wasserbau (Flow Simulation in Hydraulic Engineering), 2006
Schleppspannungsverminderung wurden für verschiedene Temperaturen und Rohrdurchmesser durchgeführ... more Schleppspannungsverminderung wurden für verschiedene Temperaturen und Rohrdurchmesser durchgeführt. Zeitgleich wurden Messungen zur räumlichen Geschwindigkeitsverteilung an der Tensidströmung mit der Hilfe eines PIV-Systems (particle image velocimetry) durchgeführt.
Some additives in solutions (polymers or surfactants, for example) can reduce the friction coeffi... more Some additives in solutions (polymers or surfactants, for example) can reduce the friction coefficient in turbulent flow compared to the water flow (up to 80%). Several parameters such as temperature, concentration and the addition or not of contre-ions were largely studied, but this is not the case of the diameter: this is the subject of this study. The pressure drop and the vortex structures are studied with field measurements obtained by PIV. Mots clefs : reduction de la trainee, additifs, turbulence, frottement.
The pattern formation and stability of a drag reducing fluid in a Taylor-Couette geometry is stud... more The pattern formation and stability of a drag reducing fluid in a Taylor-Couette geometry is studied here by Direct Numerical Simulation. When compared to the Newtonian case, DNS experiments performed on this fluid (shear-thinning with a local shear thickening) show differences in the transition from the Taylor Vortex Flow to the Fully Turbulent Flow : the Wavy Vortex Flow and Modulated Vortices Flow are inhibited and replaced by a disturbed TVF and the Turbulent Taylor Vortex flow presents only two non-circular cells. Furthermore, the larger values of Ref for the drag-reducing fluid, compared to the values of Re in the Newtonian fluid, indicate a delay in the appearance of the turbulence.
Http Www Theses Fr, 1989
Une etude par diffusion elastique et quasi-elastique de la lumiere a ete realisee sur deux sortes... more Une etude par diffusion elastique et quasi-elastique de la lumiere a ete realisee sur deux sortes de dispersions colloidales: des solutions de micelles cylindriques geantes formees a partir de tensioactifs cationiques en presence de sel, et des dispersions de particules metalliques stabilisees par des tensioactifs. Les variations en fonction de la fraction volumique de la phase dispersee et de la temperature, du coefficient de diffusion cooperatif et de l'intensite diffusee, par des solutions aqueuses micellaires de chlorure de cetyltrimethylammonium en presence de chlorure de sodium sont etudiees
Les Cahiers De Rheologie, 1996
Nous montrons les resultats d'un modele microscopique pour les micelles vermiculaires, etudie... more Nous montrons les resultats d'un modele microscopique pour les micelles vermiculaires, etudie par dynamique moleculaire hors equilibre et simule par ordinateur. Le modele 'FENE-C' introduit le processus de cassure-recombinaison dans le modele classique 'multibead spring chain model'. Nous comparons les resultats des simulations avec les predictions des theories mesoscopiques. A l'equilibre, une distribution en exponentielle de la longueur micellaire et une dependance en exponentielle de la longueur moyenne en fonction de l'energie de scission ont ete trouvees. Ces resultats correspondent aux predictions des theories mesoscopiques. L'effet du cisaillement sur la distribution de la taille et sur la longueur moyenne des micelles est reporte et discute. Les anisotropies structurales sous ecoulement sont analysees en terme de facteurs de structure statiques des particules micellaires.
Certaines solutions d'additifs (polymères ou surfactants par exemple) ont le pouvoir de rédui... more Certaines solutions d'additifs (polymères ou surfactants par exemple) ont le pouvoir de réduire le coefficient de frottement en écoulement turbulent comparé à l'écoulement du solvant pur. Dans cette contribution, on abordera l'influence des solutions de CTAC sur la réduction de la traînée en régime turbulent par la mesure des pertes de charge (frottement) et par l'étude de la turbulence (organisation de l'écoulement).
Journal de Physique II, 1997
Physical Review E, 1997
This work reports a rheological study on concentrated solutions of cethyltrimethylammonium chlori... more This work reports a rheological study on concentrated solutions of cethyltrimethylammonium chloride (CTAC) and sodium salicylate (NaSal) at a fixed molar concentration ratio [NaSal]/[CTAC]=0.6. While all the solutions behave as a Maxwell fluid, the measured zero-...
Journal of Non-Newtonian Fluid Mechanics, 2011
Some additives, like surfactants or polymers, in aqueous solutions lead to dramatic drag reducing... more Some additives, like surfactants or polymers, in aqueous solutions lead to dramatic drag reducing effects. Classically the range of concentration of surfactant additive is greater than 500 ppm. It was recently demonstrated that an aqueous solution of CTAC/NaSal (cetyltrimethyl ammonium chloride and sodium salicylate) with a concentration lower than 100 ppm has been found to reduce drag. In this work, the influence of temperature (10-50 • C) and concentration (25-150 ppm) on the drag reduction is studied with an experimental setup. A cross analysis is made from those results. It reinforces the link between the structure of the micelles (rod-like shape) and the drag reduction rate.
Journal of Non-Newtonian Fluid Mechanics, 2007
The aim of this paper is to study by direct numerical simulation the effect of a shear-thickening... more The aim of this paper is to study by direct numerical simulation the effect of a shear-thickening behaviour of a surfactant solution, on the fluid flow, and especially on the friction coefficient in a plane channel flow. A three-dimensional model named Surfactant Drag Reduction ...
Journal of Food Engineering, 2011
IRBM, 2007
The risk of nosocomial infection during surgical operations is one of the main reasons leading to... more The risk of nosocomial infection during surgical operations is one of the main reasons leading to the development of powerful techniques of ventilation within the framework of the operating theatre. During the two last decades, computational fluids dynamics (CFD) have being rapidly expanding. Nowadays it is becoming a tool usually requested to predict the airflow into furnished enclosures. However, CFD
Colloid & Polymer Science, 1999
Building and Environment, 2011
The main parameters which control the emission of volatile organic compounds between wall materia... more The main parameters which control the emission of volatile organic compounds between wall materials and indoor air were examined. A physically based model considers that the global emission phenomenon results from three elementary physical phenomena: diffusion through the boundary layer separating the wall from environment, diffusion within the porous network of the materials, and sorption of the gas molecules on the active sites of the materials. The pollutant transfer between porous material and air is therefore subjected to two complementary resistances and we identify first the resistance which controls the transfer. Then, we predict the global emission time constant from the mass transfer coefficient of convection and the thickness of the material. Experimental results from a small scale chamber are compared to predicted values in the case of acetone emission from chipboard in humid air and for high initial acetone concentration. Good agreement is obtained at the beginning of emission but an acetone retention effect by chipboard is observed, showing that it will be necessary to take into account the interactions of water vapor with materials and the pollutants to achieve accurate modeling of the material VOC emission process.
arer.org
Résumé : Les différents phénomènes physiques élémentaires qui interviennent dans le processus glo... more Résumé : Les différents phénomènes physiques élémentaires qui interviennent dans le processus global de transfert de polluant entre une paroi et l'ambiance (processus d'émission si le polluant est initialement présent dans la paroi ou effet dit de puits s'il est initialement présent dans ...
RÉSUMÉ. Cet article traite d'une étude expérimentale et d'une approche théorique de l&#... more RÉSUMÉ. Cet article traite d'une étude expérimentale et d'une approche théorique de l'influence de l'humidité sur les phénomènes de sorption d'acétone par du bois aggloméré (ce matériau est couramment utilisé, notamment en aménagement intérieur, et son processus de ...
Comptes Rendus Mécanique, 2010