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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

Intensification of the dissolution of a sparingly soluble solid from a spinning disk in the presence of power ultrasound / D. Krishna Sandilya 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. 13083–13091 Titre : Intensification of the dissolution of a sparingly soluble solid from a spinning disk in the presence of power ultrasound Type de document : texte imprimé Auteurs : D. Krishna Sandilya, Auteur ; A. Kannan, Auteur Année de publication : 2012 Article en page(s) : pp. 13083–13091 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Power  ultrasound Résumé : The effect of power ultrasound (20 kHz) on the dissolution rates of a spinning disk made from sparingly soluble benzoic acid was investigated. Ultrasound was found to intensify the dissolution rates especially at lower rotational speeds of the spinning disk. The ultrasonic intensification was found to decrease with increase in the rotational speed of the spinning disk. Empirical correlation was developed for the Sherwood number in the presence of ultrasound and mechanical rotation of the disk. From this, the intensification factor was derived in terms of ultrasonic power input and Reynolds number corresponding to the spinning disk. The intensification factor obtained in the current spinning disk configuration was compared with that obtained for the rotating cylinder configuration studied by Kannan and Pathan [Kannan, A.; Pathan, S. K. Enhancement of Solid Dissolution Process. Chem. Eng. J.2004, 102, 45.]. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101702u [article] Intensification of the dissolution of a sparingly soluble solid from a spinning disk in the presence of power ultrasound [texte imprimé] / D. Krishna Sandilya, Auteur ; A. Kannan, Auteur . - 2012 . - pp. 13083–13091. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 13083–13091 Mots-clés : Power  ultrasound Résumé : The effect of power ultrasound (20 kHz) on the dissolution rates of a spinning disk made from sparingly soluble benzoic acid was investigated. Ultrasound was found to intensify the dissolution rates especially at lower rotational speeds of the spinning disk. The ultrasonic intensification was found to decrease with increase in the rotational speed of the spinning disk. Empirical correlation was developed for the Sherwood number in the presence of ultrasound and mechanical rotation of the disk. From this, the intensification factor was derived in terms of ultrasonic power input and Reynolds number corresponding to the spinning disk. The intensification factor obtained in the current spinning disk configuration was compared with that obtained for the rotating cylinder configuration studied by Kannan and Pathan [Kannan, A.; Pathan, S. K. Enhancement of Solid Dissolution Process. Chem. Eng. J.2004, 102, 45.]. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101702u