Natural convection between two concentric spheres: transition toward a multicellular flow

A moderate temperature difference maintained between two concentric spherical surfaces induces, in steady state, unicellular toroidal movements in the enclosed fluid. Beyond a critical temperature difference, the flow becomes unstable and the convective phenomena rearrange into counter-rotating toroidal cells. A two-dimensional axisymmetric numerical model confirms the existence of a unicellular regime and shows that, beyond the critical conditions and for the same set of parameters, two convergent solutions can be obtained. One is unicellular and the other is bicellular; in the latter, the additional cell appears at the top of the layer. The initial conditions determine which one of these two will be established. This transition is investigated as a function of several parameters and the results are compared with the experimental results in the literature

Thermal instability in a porous medium with random vibrations

Onset of thermal convection in a layer of saturated porous medium, heated from below, is examined when the layer is subjected to random vibrations. It is shown that when the vibrations are characterized by a white noise process, they hasten the onset of convection. Further, decrease in permeability tends to stabilize the flow field.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41712/1/707_2005_Article_BF01175814.pd

Les méthodes thermiques de production des hydrocarbures. Chapitre 3 : Injection de fluides chauds. Principes et études de laboratoire

Après avoir indiqué les principes des différents procédés de déplacement ou de stimulation faisant appel à l'injection de fluides chauds, eau liquide ou vapeur d'eau, on détaille les mécanismes physiques mis en jeu par ces procédés en indiquant les facteurs limitant l'application des méthodes étudiées. On donne ensuite les résultats d'une étude comparative de la stabilité de ces déplacements avant d'apporter quelques précisions sur les questions de récupération d'huile et d'efficacité de balayage

Les méthodesthermiques de production des hydrocarbures. Chapitre 1 : transfert de chaleur et de masse

Après un rappel général sur le transfert de chaleur et de masse ainsi que sur les lois de conservation dans les milieux continus, on traite de l'adaptation de ces lois au cas des milieux poreux. On donne ensuite des informations quantitatives sur les grandeurs physiques mises en jeu par les phénomènes de transfert en milieu poreux

Les méthodesthermiques de production des hydrocarbures. Chapitre 1 : transfert de chaleur et de masse Thermal Methods of Hydrocarbon Production. Chapter 1 : Heat and Mass Transfer

Après un rappel général sur le transfert de chaleur et de masse ainsi que sur les lois de conservation dans les milieux continus, on traite de l'adaptation de ces lois au cas des milieux poreux. On donne ensuite des informations quantitatives sur les grandeurs physiques mises en jeu par les phénomènes de transfert en milieu poreux. After making a general review of heat and mass transfer a well as of laws of conservation in continua, this chapter describes how these laws con be adopted to the case of porous media. Quantitative data are then given on the physical magnitudes brought into play by transfer phenomena in porous media

Les méthodes thermiques de production des hydrocarbures. Chapitre2 : Transformations physiques et chimiques des hydrocarbures et de l'eau

On rappelle des notions sur les phénomènes de changement d'état et sur les réactions chimiques susceptibles d'intervenir lors de l'utilisation des méthodes thermiques

Equine follicle-stimulating hormone. Purification, acid dissociation, and binding to equine testicular tissue.

International audienceA simple method of purification of equine follicle-stimulating hormone is described by which two forms of the hormone are obtained. The acid dissociation of the most active preparation was studied and a pKa of 5.8 was determined at 37 degrees C. This value is 2 pH units higher than that observed for pregnant mare serum gonadotropin suggesting that the binding areas between subunits are not identical in the two hormones. We also describe an homologous radioreceptor assay of equine follicle-stimulating hormone which is highly specific for this hormone in contrast to the heterologous systems described so far. The analysis of the properties of equine gonadotropins in homologous and heterologous radioreceptor assays suggests that all glycoprotein hormones share a common high affinity binding site and that specificity of binding is due to binding prohibition sites preventing fixation of each hormone to the receptors of the other glycoprotein hormones. This specific hindering is defined as "negative specificity.