Development of a combined solver to model transport and chemical reactions in catalytic wall-flow filters

none5siIn this work, we develop a non-isothermal model for diesel particulate filters including exothermic and competing chemical reactions. We begin with an isothermal, single-reaction model and we gradually increase its complexity. By comparing various models, we aim at establishing the minimum degree of complexity required to effectively model the system under investigation. Based on the numerical simulations, we conclude that isothermal models are adequate only if the temperature of the catalyst is, at all times, completely below or completely above a critical temperature. However, if the goal is to predict the critical temperature, only non-isothermal models should be used. The results with competing reactions, on the other hand, show that the presence of competing reactions does not affect significantly the overall conversion in the filter.noneAllouche M.H.; Enjalbert R.; Alberini F.; Ariane M.; Alexiadis A.Allouche M.H.; Enjalbert R.; Alberini F.; Ariane M.; Alexiadis A

Etude expérimentale de la stabilité de l'écoulement de films de fluide non Newtonien sur plan incliné

Nous étudions la stabilité de l'écoulement de films de fluide rhéofluidifiant (pseudoplastique) sur plan incliné. Nous modélisons la viscosité des fluides utilisés par la loi de Carreau. Afin de caractériser nos fluides, nous utilisons l'électrocapillarité comme technique optique consistant à étudier la propagation et l'atténuation d'ondes capillaires. Les résultats de mesures permettent en particulier de déterminer la viscosité à des valeurs de cisaillement aussi faibles que 10-3 s-1. Notre objectif est d'étudier expérimentalement la stabilité de films rhéofluidifiants sur plan incliné. Pour des valeurs fixées de l'angle d'inclinaison, nous avons déterminé le seuil critique expérimental et tracé la courbe marginale de stabilité sur les plans (Re, f) et (Re, k) pour nos différents fluides. Nous trouvons que nos résultats expérimentaux sont en bon accord avec les résultats numériques, et confirment l'effet rhéofluidifiant déstabilisant relativement au cas Newtonien

Étude théorique et expérimentale de la stabilité de l'écoulement de films de fluide non Newtonien sur plan incliné

We study the stability of shear-thinning (pseudoplastic) fluid films flow down an inclined plane. This problem is of interest in many industrial applications such as coating, and may explain the manifestation of a specific kind of surface waves, appearing in some spectacular environmental flow configurations such as debris flows or surge waves. We focus on fluids obeying the Carreau law. An optical technique called electrocapillarity has been implemented in order to determine the surface tension and viscosity, at values of the shear rate as small as 10−3s−1, by studying the damping of propagating capillary waves. The main objective of this work is to experimentally study the linear stability of shear-thinning fluid films flow. For a fixed inclination angle, the experimental study essentially consists in measuring the cutoff frequency and wavelength of primary waves, and then determining the critical Reynolds number. The experimental results presented in the (Re, k) and (Re, c) planes are in good agreement with the numerical results, and confirm the destabilizing effect of the shear-thinning properties in comparison with the Newtonian case (the critical Reynolds number is smaller, and the ratio between the marginal waves celerity and the flow velocity at the free surface is larger). Finally, we discuss the validity of the Squire’s theorem in the case of generalized Newtonian fluids film flow down an inclined plane. Analytically, the Orr-Sommerfeld problem with respect to 3D disturbances is not equivalent to a 2D problem, and the numerical results show that the Squire’s transformations can only be used in the Newtonian caseNous étudions la stabilité de l'écoulement de fluide rhéofluidifiant (pseudoplastique) sur plan incliné. La connaissance des conditions d'apparition des instabilités intéresse ici particulièrement le secteur industriel faisant appel à des méthodes de couchage (papeterie, photographie), ou le secteur environnemental dans la compréhension de certaines situations exceptionnelles (coulées de boues, laves torrentielles, écoulements de glaciers). Nous modélisons la viscosité des fluides utilisés par la loi de Carreau. Afin de caractériser nos fluides, nous utilisons l'électrocapillarité comme technique optique consistant à étudier la propagation et l'atténuation d'ondes capillaires. Les résultats de mesures permettent en particulier de déterminer la viscosité à valeur de cisaillement aussi faibles que 10−3s−1. Notre objectif est d'étudier expérimentalement la stabilité de films rhéofluidifiants sur plan incliné. Pour des valeurs fixées de l'angle d'inclinaison, nous avons déterminé le seuil critique expérimental et tracé la courbe marginale de stabilité sur les plans (Re, k) et (Re, c) pour nos différents fluides. Nous trouvons que nos résultats expérimentaux sont en bon accord avec les résultats numériques, et confirment l'effet rhéofluidifiant déstabilisant relativement au cas Newtonien. Nous discutons enfin la validité du théorème de Squire en écrivant l'équation d'Orr-Sommerfeld généralisée aux ondes 3D et aux fluides de Carreau. Analytiquement, les relations de Squire ne sont pas vérifiées, et les résultats numériques montrent que les relations de Squire ne s'écrivent que dans le cas Newtonie

Theoretical and experimental study of the stability of non Newtonian fluid films flowing down an inclined plane

Nous étudions la stabilité de l'écoulement de fluide rhéofluidifiant (pseudoplastique) sur plan incliné. La connaissance des conditions d'apparition des instabilités intéresse ici particulièrement le secteur industriel faisant appel à des méthodes de couchage (papeterie, photographie), ou le secteur environnemental dans la compréhension de certaines situations exceptionnelles (coulées de boues, laves torrentielles, écoulements de glaciers). Nous modélisons la viscosité des fluides utilisés par la loi de Carreau. Afin de caractériser nos fluides, nous utilisons l'électrocapillarité comme technique optique consistant à étudier la propagation et l'atténuation d'ondes capillaires. Les résultats de mesures permettent en particulier de déterminer la viscosité à valeur de cisaillement aussi faibles que 10−3s−1. Notre objectif est d'étudier expérimentalement la stabilité de films rhéofluidifiants sur plan incliné. Pour des valeurs fixées de l'angle d'inclinaison, nous avons déterminé le seuil critique expérimental et tracé la courbe marginale de stabilité sur les plans (Re, k) et (Re, c) pour nos différents fluides. Nous trouvons que nos résultats expérimentaux sont en bon accord avec les résultats numériques, et confirment l'effet rhéofluidifiant déstabilisant relativement au cas Newtonien. Nous discutons enfin la validité du théorème de Squire en écrivant l'équation d'Orr-Sommerfeld généralisée aux ondes 3D et aux fluides de Carreau. Analytiquement, les relations de Squire ne sont pas vérifiées, et les résultats numériques montrent que les relations de Squire ne s'écrivent que dans le cas NewtonienWe study the stability of shear-thinning (pseudoplastic) fluid films flow down an inclined plane. This problem is of interest in many industrial applications such as coating, and may explain the manifestation of a specific kind of surface waves, appearing in some spectacular environmental flow configurations such as debris flows or surge waves. We focus on fluids obeying the Carreau law. An optical technique called electrocapillarity has been implemented in order to determine the surface tension and viscosity, at values of the shear rate as small as 10−3s−1, by studying the damping of propagating capillary waves. The main objective of this work is to experimentally study the linear stability of shear-thinning fluid films flow. For a fixed inclination angle, the experimental study essentially consists in measuring the cutoff frequency and wavelength of primary waves, and then determining the critical Reynolds number. The experimental results presented in the (Re, k) and (Re, c) planes are in good agreement with the numerical results, and confirm the destabilizing effect of the shear-thinning properties in comparison with the Newtonian case (the critical Reynolds number is smaller, and the ratio between the marginal waves celerity and the flow velocity at the free surface is larger). Finally, we discuss the validity of the Squire’s theorem in the case of generalized Newtonian fluids film flow down an inclined plane. Analytically, the Orr-Sommerfeld problem with respect to 3D disturbances is not equivalent to a 2D problem, and the numerical results show that the Squire’s transformations can only be used in the Newtonian cas

Stability of a flow down an incline with respect to two-dimensional disturbances for Newtonian and non-Newtonian fluids

International audienceSquire's theorem, which states that the two-dimensional instabilities are more dangerous than the three-dimensional instabilities, is revisited here for a flow down an incline, making use of numerical stability analysis and Squire relationships when available. For flows down inclined planes, one of these Squire relationships involves the slopes of the inclines. This means that the Reynolds number associated with a two-dimensional wave can be shown to be smaller than that for an oblique wave, but this oblique wave being obtained for a larger slope. Physically speaking, this prevents the possibility to directly compare the thresholds at a given slope. The goal of the paper is then to reach a conclusion about the predominance or not of two-dimensional instabilities at a given slope, which is of practical interest for industrial or environmental applications. For a Newtonian fluid, it is shown that, for a given slope, oblique wave instabilities are never the dominant instabilities. Both the Squire relationships and the particular variations of the two-dimensional wave critical curve with regard to the inclination angle are involved in the proof of this result. For a generalized Newtonian fluid, a similar result can only be obtained for a reduced stability problem where some term connected to the perturbation of viscosity is neglected. For the general stability problem, however, no Squire relationships can be derived and the numerical stability results show that the thresholds for oblique waves can be smaller than the thresholds for two-dimensional waves at a given slope, particularly for large obliquity angles and strong shear-thinning behaviors. The conclusion is then completely different in that case: the dominant instability for a generalized Newtonian fluid flowing down an inclined plane with a given slope can be three dimensional

Dispositif expérimental pour l'étude d'ondes à la surface de films non-Newtoniens s'écoulant sur un plan incliné

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Stability of a flow down an incline with respect to two-dimensional disturbances for Newtonian and non-Newtonian fluids

International audienceSquire's theorem, which states that the two-dimensional instabilities are more dangerous than the three-dimensional instabilities, is revisited here for a flow down an incline, making use of numerical stability analysis and Squire relationships when available. For flows down inclined planes, one of these Squire relationships involves the slopes of the inclines. This means that the Reynolds number associated with a two-dimensional wave can be shown to be smaller than that for an oblique wave, but this oblique wave being obtained for a larger slope. Physically speaking, this prevents the possibility to directly compare the thresholds at a given slope. The goal of the paper is then to reach a conclusion about the predominance or not of two-dimensional instabilities at a given slope, which is of practical interest for industrial or environmental applications. For a Newtonian fluid, it is shown that, for a given slope, oblique wave instabilities are never the dominant instabilities. Both the Squire relationships and the particular variations of the two-dimensional wave critical curve with regard to the inclination angle are involved in the proof of this result. For a generalized Newtonian fluid, a similar result can only be obtained for a reduced stability problem where some term connected to the perturbation of viscosity is neglected. For the general stability problem, however, no Squire relationships can be derived and the numerical stability results show that the thresholds for oblique waves can be smaller than the thresholds for two-dimensional waves at a given slope, particularly for large obliquity angles and strong shear-thinning behaviors. The conclusion is then completely different in that case: the dominant instability for a generalized Newtonian fluid flowing down an inclined plane with a given slope can be three dimensional

Experimental determination of the viscosity at very low shear rate for shear thinning fluids by electrocapillarity

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Corrigendum to "Development of a combined solver to model transport and chemical reactions in catalytic wall-flow filters" [Chem. Eng. Res. Des. 117 (2016) 681-687]

none7siThe authors regret that two of the authors, Li Liu and Sam K. Wilkinson, were omitted in error during the publication of this article. Hence the full list of authors is now shown in this corrigendum. The authors would like to apologise for any inconvenience caused.noneAllouche M.H.; Enjalbert R.; Alberini F.; Ariane M.; Liu L.; Wilkinson S.K.; Alexiadis A.Allouche M.H.; Enjalbert R.; Alberini F.; Ariane M.; Liu L.; Wilkinson S.K.; Alexiadis A

Stability of a generalized Newtonian fluid film flowing down an inclined plane with respect to two-dimensional and three-dimensional disturbances

International audienceCITATIONS 0 READS 64 7 authors, including: Some of the authors of this publication are also working on these related projects