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Effects of particle blockage and eccentricity in location on the non-newtonian fluid hydrodynamics around a sphere / Suresh Krishnan in Industrial & engineering chemistry research, Vol. 51 N° 45 (Novembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 45 (Novembre 2012) . - pp. 14867-14883 Titre : Effects of particle blockage and eccentricity in location on the non-newtonian fluid hydrodynamics around a sphere Type de document : texte imprimé Auteurs : Suresh Krishnan, Auteur ; A. Kannan, Auteur Année de publication : 2013 Article en page(s) : pp. 14867-14883 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Hydrodynamics  Non  Newtonian  fluid Résumé : The flow of an incompressible non-Newtonian fluid over an eccentrically located sphere confined in a circular tube was investigated using three-dimensional steady state Computational Fluid Dynamics simulations. Pseudoplastic fluids with different power-law indices of 0.57, 0.76, and 0.94 were considered. The effects of ratio of particle diameter to tube diameter (blockage ratio, BR) and ratio of offset of the sphere position from the tube axis to the tube radius (eccentricity, Ec) on the hydrodynamic phenomena around the sphere are reported over a range of particle Reynolds numbers (Rep). The simulations were carried out in the range (0.1 ≤ Rep ≤ 40, 0.01 ≤ BR ≤ 0.5, and 0.0 ≤ Ec ≤ 0.6). The drag coefficient predictions for an unconfined sphere were found to be sensitive to the value of the consistency index parameter (K) in the viscous flow regime, especially at lower n values. At lower particle Reynolds numbers and centrally located sphere, the enhancement in drag coefficient due to blockage ratio was felt least by the fluid with the lowest n value. Even at higher Rep, higher blockage ratios still could cause significant enhancements in the drag coefficients (∼20%) for centrally located spheres. Irrespective of the power-law index, eccentric location of the sphere caused a decline in the overall drag coefficient due to the dominant influence of the lower hemisphere which was closer to the tube wall. At the highest particle Reynolds numbers, eccentricity, and blockage ratio, asymmetric fluid flow distribution caused opposing effects by decreasing the viscous drag coefficient and increasing the form drag coefficient relative to those obtained with the centrally confined sphere. Sharp variations in the shear rate dependent viscosity at the sphere surface could be associated with boundary layer separation. Wall effects at higher blockage ratio suppressed the boundary layer separation in the case of the fluid with the highest power-law index. Eccentricity also caused accelerated boundary layer separation at the upper hemisphere and absence of boundary layer separation along the lower hemisphere. At lower blockage ratios a maximum in the lift coefficient versus particle Reynolds number was usually observed. This study will be relevant in applications such as aseptic food processing, petroleum well drilling, fluidization, and particle transport in microfluidic devices. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26620400 [article] Effects of particle blockage and eccentricity in location on the non-newtonian fluid hydrodynamics around a sphere [texte imprimé] / Suresh Krishnan, Auteur ; A. Kannan, Auteur . - 2013 . - pp. 14867-14883. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 45 (Novembre 2012) . - pp. 14867-14883 Mots-clés : Hydrodynamics  Non  Newtonian  fluid Résumé : The flow of an incompressible non-Newtonian fluid over an eccentrically located sphere confined in a circular tube was investigated using three-dimensional steady state Computational Fluid Dynamics simulations. Pseudoplastic fluids with different power-law indices of 0.57, 0.76, and 0.94 were considered. The effects of ratio of particle diameter to tube diameter (blockage ratio, BR) and ratio of offset of the sphere position from the tube axis to the tube radius (eccentricity, Ec) on the hydrodynamic phenomena around the sphere are reported over a range of particle Reynolds numbers (Rep). The simulations were carried out in the range (0.1 ≤ Rep ≤ 40, 0.01 ≤ BR ≤ 0.5, and 0.0 ≤ Ec ≤ 0.6). The drag coefficient predictions for an unconfined sphere were found to be sensitive to the value of the consistency index parameter (K) in the viscous flow regime, especially at lower n values. At lower particle Reynolds numbers and centrally located sphere, the enhancement in drag coefficient due to blockage ratio was felt least by the fluid with the lowest n value. Even at higher Rep, higher blockage ratios still could cause significant enhancements in the drag coefficients (∼20%) for centrally located spheres. Irrespective of the power-law index, eccentric location of the sphere caused a decline in the overall drag coefficient due to the dominant influence of the lower hemisphere which was closer to the tube wall. At the highest particle Reynolds numbers, eccentricity, and blockage ratio, asymmetric fluid flow distribution caused opposing effects by decreasing the viscous drag coefficient and increasing the form drag coefficient relative to those obtained with the centrally confined sphere. Sharp variations in the shear rate dependent viscosity at the sphere surface could be associated with boundary layer separation. Wall effects at higher blockage ratio suppressed the boundary layer separation in the case of the fluid with the highest power-law index. Eccentricity also caused accelerated boundary layer separation at the upper hemisphere and absence of boundary layer separation along the lower hemisphere. At lower blockage ratios a maximum in the lift coefficient versus particle Reynolds number was usually observed. This study will be relevant in applications such as aseptic food processing, petroleum well drilling, fluidization, and particle transport in microfluidic devices. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26620400

Effects of particle diameter and position on hydrodynamics around a confined sphere / Suresh Krishnan in Industrial & engineering chemistry research, Vol. 50 N° 23 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 13137–13160 Titre : Effects of particle diameter and position on hydrodynamics around a confined sphere Type de document : texte imprimé Auteurs : Suresh Krishnan, Auteur ; Kannan Aravamudan, Auteur Année de publication : 2012 Article en page(s) : pp. 13137–13160 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Hydrodynamics Résumé : The effect of confinement of a sphere within a tube on the hydrodynamics of Newtonian fluid flow around the solid surface is investigated. The ratio of particle diameter to tube diameter (blockage ratio), the ratio of sphere distance from the tube axis to the tube diameter (eccentricity), and the fluid flow rate were the parameters of this study. Computational fluid dynamics (CFD) simulations were carried out to obtain the flow field around the sphere from which the angle of boundary layer separations, as well as drag and lift coefficients, were obtained. The pressure distributions and friction factor along the sphere surface are also reported. To estimate the effect of confinement and eccentricity in position of the particle, with respect to the tube axis, the results are compared with the classical case involving the flow of an unbounded fluid over the sphere. The drag coefficient diminished when the particle was positioned eccentrically with respect to the tube axis at very low particle Reynolds number (Rep). However, the drag coefficient increased with increasing eccentric positions at higher Rep. At eccentric particle positions, boundary layer separation occurred earlier from the upper hemisphere while, depending on the eccentricity, it was delayed or nonexistent in the lower hemisphere. The difference in pressure between the lower and upper hemisphere regions led to incursion of fluid into the upper hemispherical region. Correlations are proposed for the drag and lift coefficients in the range of 0.1≤ Rep ≤ 500 for different possible eccentricities and blockage ratios. The results from this work will be of relevance in applications such as fluidization and aseptic food processing. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2000852 [article] Effects of particle diameter and position on hydrodynamics around a confined sphere [texte imprimé] / Suresh Krishnan, Auteur ; Kannan Aravamudan, Auteur . - 2012 . - pp. 13137–13160. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 13137–13160 Mots-clés : Hydrodynamics Résumé : The effect of confinement of a sphere within a tube on the hydrodynamics of Newtonian fluid flow around the solid surface is investigated. The ratio of particle diameter to tube diameter (blockage ratio), the ratio of sphere distance from the tube axis to the tube diameter (eccentricity), and the fluid flow rate were the parameters of this study. Computational fluid dynamics (CFD) simulations were carried out to obtain the flow field around the sphere from which the angle of boundary layer separations, as well as drag and lift coefficients, were obtained. The pressure distributions and friction factor along the sphere surface are also reported. To estimate the effect of confinement and eccentricity in position of the particle, with respect to the tube axis, the results are compared with the classical case involving the flow of an unbounded fluid over the sphere. The drag coefficient diminished when the particle was positioned eccentrically with respect to the tube axis at very low particle Reynolds number (Rep). However, the drag coefficient increased with increasing eccentric positions at higher Rep. At eccentric particle positions, boundary layer separation occurred earlier from the upper hemisphere while, depending on the eccentricity, it was delayed or nonexistent in the lower hemisphere. The difference in pressure between the lower and upper hemisphere regions led to incursion of fluid into the upper hemispherical region. Correlations are proposed for the drag and lift coefficients in the range of 0.1≤ Rep ≤ 500 for different possible eccentricities and blockage ratios. The results from this work will be of relevance in applications such as fluidization and aseptic food processing. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2000852