Nouvelle avancee dans la maitrise des procedes d'ultrafiltration : acces au gradient de conce... more Nouvelle avancee dans la maitrise des procedes d'ultrafiltration : acces au gradient de concentration par mesure locale in-situ de diffusion de rayons x aux petits angles. Application aux micelles de caseines.
Mixing of viscous non‐Newtonian fluids plays an important role in many industrial processes (wast... more Mixing of viscous non‐Newtonian fluids plays an important role in many industrial processes (wastewater treatment, methanization, etc.). In some cases, mixing by gas injection can be more interesting than mechanical mixing. The present study focuses on the gas injection in yield stress fluids. The influence of the air flow rate, fluid rheological properties, and geometrical configuration on an air jet impinging the bottom wall of a tank containing a yield stress fluid has been considered. Focus has been placed on the air cavity present at the injection point. The trends of two key parameters of the cavity have been characterized: its maximum diameter and frequency detachment. Correlations based on the characteristic dimensionless numbers governing the flow have been derived. These correlations show that the apparent viscosity has an effect on the cavity's frequency but a low influence on its diameter which is mainly governed by the air flow inertia.
Correlation between the variations of coiling of heteromorphic ammonites of the same lineage and ... more Correlation between the variations of coiling of heteromorphic ammonites of the same lineage and the sea level variations is pointed out by studying the examples of Tropaeum from Aptian and of Heteroceras from Upper Barremian. The uncoiling of shell is more enhanced during the transgressive periods. During the regressive periods, normal involution coiling is favoured. These morphological transformations appear to be an adaptive mechanism against sea events. Morpho-functional and mechanical analyses give an explanation of this mechanism
In this paper, we propose to explore experimentally the origin of the onset of motion in a well-k... more In this paper, we propose to explore experimentally the origin of the onset of motion in a well-known Carbopol gel, a concentrated suspension of microgels, when submitted to a vertical temperature gradient, namely, the Rayleigh-Bénard Convection (RBC). We consider three possible scenarios: (i) the gel behaves as an elasto-viscoplastic material, (ii) the gel presents a low-stress viscosity μ+ below the yield stress τy, and (iii) the gel can be considered as a two phase system, say the microgels and the solvent, i.e., a porous medium. We propose a complete rheological characterization of Carbopol 940. Creep measurements lead to obtain an instantaneous viscosity plateau μ+∼tm with m≈1. For the first time, we measure and provide permeability values k in the Carbopol gels. We show that k = O(10−14) m2 and k∝τy0.2. Our study focuses on the reference case of the RBC with no-slip conditions at walls, and new results are provided. The results lead to the conclusion that the control parameter...
On considère l’écoulement rampant d’un fluide à seuil autour d’un cylindre en milieu infini. Plus... more On considère l’écoulement rampant d’un fluide à seuil autour d’un cylindre en milieu infini. Plusieurs rugosités ont été considérées afin de mettre en évidence l’influence du glissement et de l’adhérence à l’interface fluide cylindre.Les influences des conditions à l’interface cylindre-fluide, et du nombre d’Oldroyd, (rapport des effets plastiques aux effets visqueux) sur le coefficient de traînée sont mises en évidence. La détermination des champs devitesse par PIV permet de comprendre le comportement local du fluide en fonction de la présence ou non de glissementà la paroi du cylindre.
Volume 2: Symposia and General Papers, Parts A and B, 2002
The laminar isothermal mixing of a viscoplastic fluid is considered in the absence of any free su... more The laminar isothermal mixing of a viscoplastic fluid is considered in the absence of any free surface and when the material can be modelled using a Bingham constitutive equation. The material is mixed by a rotating cylindrical tank and a fixed anchor impeller. A two-dimensional numerical simulation is performed with a finite elements method. The effects of viscoplasticity and inertia are related to an Oldroyd (Od) and to a Reynolds (Re) number. Stream lines, vortices, yield surfaces and power consumption are shown and analysed depending on the value of Od and Re parameters.
Many of us have anticipated a book dealing with contemporary art of Africa which would offer new ... more Many of us have anticipated a book dealing with contemporary art of Africa which would offer new information about outstanding artists and highlight some of the finest art of the continent. Such a publication, one imagined, would bring pride and understanding to a ...
Nouvelle avancee dans la maitrise des procedes d'ultrafiltration : acces au gradient de conce... more Nouvelle avancee dans la maitrise des procedes d'ultrafiltration : acces au gradient de concentration par mesure locale in-situ de diffusion de rayons x aux petits angles. Application aux micelles de caseines.
Mixing of viscous non‐Newtonian fluids plays an important role in many industrial processes (wast... more Mixing of viscous non‐Newtonian fluids plays an important role in many industrial processes (wastewater treatment, methanization, etc.). In some cases, mixing by gas injection can be more interesting than mechanical mixing. The present study focuses on the gas injection in yield stress fluids. The influence of the air flow rate, fluid rheological properties, and geometrical configuration on an air jet impinging the bottom wall of a tank containing a yield stress fluid has been considered. Focus has been placed on the air cavity present at the injection point. The trends of two key parameters of the cavity have been characterized: its maximum diameter and frequency detachment. Correlations based on the characteristic dimensionless numbers governing the flow have been derived. These correlations show that the apparent viscosity has an effect on the cavity's frequency but a low influence on its diameter which is mainly governed by the air flow inertia.
Correlation between the variations of coiling of heteromorphic ammonites of the same lineage and ... more Correlation between the variations of coiling of heteromorphic ammonites of the same lineage and the sea level variations is pointed out by studying the examples of Tropaeum from Aptian and of Heteroceras from Upper Barremian. The uncoiling of shell is more enhanced during the transgressive periods. During the regressive periods, normal involution coiling is favoured. These morphological transformations appear to be an adaptive mechanism against sea events. Morpho-functional and mechanical analyses give an explanation of this mechanism
In this paper, we propose to explore experimentally the origin of the onset of motion in a well-k... more In this paper, we propose to explore experimentally the origin of the onset of motion in a well-known Carbopol gel, a concentrated suspension of microgels, when submitted to a vertical temperature gradient, namely, the Rayleigh-Bénard Convection (RBC). We consider three possible scenarios: (i) the gel behaves as an elasto-viscoplastic material, (ii) the gel presents a low-stress viscosity μ+ below the yield stress τy, and (iii) the gel can be considered as a two phase system, say the microgels and the solvent, i.e., a porous medium. We propose a complete rheological characterization of Carbopol 940. Creep measurements lead to obtain an instantaneous viscosity plateau μ+∼tm with m≈1. For the first time, we measure and provide permeability values k in the Carbopol gels. We show that k = O(10−14) m2 and k∝τy0.2. Our study focuses on the reference case of the RBC with no-slip conditions at walls, and new results are provided. The results lead to the conclusion that the control parameter...
On considère l’écoulement rampant d’un fluide à seuil autour d’un cylindre en milieu infini. Plus... more On considère l’écoulement rampant d’un fluide à seuil autour d’un cylindre en milieu infini. Plusieurs rugosités ont été considérées afin de mettre en évidence l’influence du glissement et de l’adhérence à l’interface fluide cylindre.Les influences des conditions à l’interface cylindre-fluide, et du nombre d’Oldroyd, (rapport des effets plastiques aux effets visqueux) sur le coefficient de traînée sont mises en évidence. La détermination des champs devitesse par PIV permet de comprendre le comportement local du fluide en fonction de la présence ou non de glissementà la paroi du cylindre.
Volume 2: Symposia and General Papers, Parts A and B, 2002
The laminar isothermal mixing of a viscoplastic fluid is considered in the absence of any free su... more The laminar isothermal mixing of a viscoplastic fluid is considered in the absence of any free surface and when the material can be modelled using a Bingham constitutive equation. The material is mixed by a rotating cylindrical tank and a fixed anchor impeller. A two-dimensional numerical simulation is performed with a finite elements method. The effects of viscoplasticity and inertia are related to an Oldroyd (Od) and to a Reynolds (Re) number. Stream lines, vortices, yield surfaces and power consumption are shown and analysed depending on the value of Od and Re parameters.
Many of us have anticipated a book dealing with contemporary art of Africa which would offer new ... more Many of us have anticipated a book dealing with contemporary art of Africa which would offer new information about outstanding artists and highlight some of the finest art of the continent. Such a publication, one imagined, would bring pride and understanding to a ...
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