Documents disponibles écrits par cet auteur

Experimental investigations of rise behavior of monodispersed / polydispersed bubbly flows in quiescent liquids / Swapna S. Rabha in Industrial & engineering chemistry research, Vol. 49 N° 21 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10615-10626 Titre : Experimental investigations of rise behavior of monodispersed / polydispersed bubbly flows in quiescent liquids Type de document : texte imprimé Auteurs : Swapna S. Rabha, Auteur ; Vivek V. Buwa, Auteur Année de publication : 2011 Article en page(s) : pp. 10615-10626 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Bubble  flow Résumé : The predictive capabilities of continuum CFD models to simulate large-scale dispersed gas—liquid flows depend on the closures used to estimate the interphase coupling forces. The present manuscript shows that different corrections that are applied to correct the drag force for multiple bubble systems lead to different predictions as the gas volume fraction is increased. In the present work, experimental investigations of monodispersed and polydispersed bubbles of different diameters (1.2 ≤ dB ≤ 7.5 mm) rising in quiescent water (0.19 ≤ Eo ≤ 8.72; log Mo = -10.5) at different gas volume fractions (0.01 < αG < 0.2) are reported. The bubble rise velocity of a single isolated bubble, a bubble rising in a single chain and bubbles rising in multiple chains were compared. The effect of bubble diameter and gas volume fraction on the fluctuations in bubble rise velocities of individual bubbles rising in multiple chains was also investigated. The rise velocities of monodispersed bubble swarms were found to increase with the increase in dB and αG. The number- and time-averaged bubble rise velocity and drag coefficient for monodispersed bubble swarms were investigated as a function of αG. The drag coefficients based on the slip velocity of the bubble swarms for αG < 0.1 were found to decrease with increase in αG and showed good agreement with the previous literature; but for αG > 0.1, the drag coefficient were found to be independent of αG. Further, the rise behavior of poly dispersed bubbles was also investigated. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447954 [article] Experimental investigations of rise behavior of monodispersed / polydispersed bubbly flows in quiescent liquids [texte imprimé] / Swapna S. Rabha, Auteur ; Vivek V. Buwa, Auteur . - 2011 . - pp. 10615-10626. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10615-10626 Mots-clés : Bubble  flow Résumé : The predictive capabilities of continuum CFD models to simulate large-scale dispersed gas—liquid flows depend on the closures used to estimate the interphase coupling forces. The present manuscript shows that different corrections that are applied to correct the drag force for multiple bubble systems lead to different predictions as the gas volume fraction is increased. In the present work, experimental investigations of monodispersed and polydispersed bubbles of different diameters (1.2 ≤ dB ≤ 7.5 mm) rising in quiescent water (0.19 ≤ Eo ≤ 8.72; log Mo = -10.5) at different gas volume fractions (0.01 < αG < 0.2) are reported. The bubble rise velocity of a single isolated bubble, a bubble rising in a single chain and bubbles rising in multiple chains were compared. The effect of bubble diameter and gas volume fraction on the fluctuations in bubble rise velocities of individual bubbles rising in multiple chains was also investigated. The rise velocities of monodispersed bubble swarms were found to increase with the increase in dB and αG. The number- and time-averaged bubble rise velocity and drag coefficient for monodispersed bubble swarms were investigated as a function of αG. The drag coefficients based on the slip velocity of the bubble swarms for αG < 0.1 were found to decrease with increase in αG and showed good agreement with the previous literature; but for αG > 0.1, the drag coefficient were found to be independent of αG. Further, the rise behavior of poly dispersed bubbles was also investigated. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447954

Numerical simulations of bubble formation and rise in microchannels / Deepak Goel in Industrial & engineering chemistry research, Vol. 48 N° 17 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8109–8120 Titre : Numerical simulations of bubble formation and rise in microchannels Type de document : texte imprimé Auteurs : Deepak Goel, Auteur ; Vivek V. Buwa, Auteur Année de publication : 2009 Article en page(s) : pp. 8109–8120 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Microchannels  Gas−liquid  flow  Bubbles Résumé : Gas−liquid flow in microchannels is of fundamental importance to many engineering applications involving microreactors, monolith reactors, microheat exchangers, and several other microfluidic devices. Slug flow, characterized by motion of long bubbles, also referred to as Taylor bubbles, is the most important of the different two-phase flow regimes observed in microchannels. In this work, the formation of bubbles and their rise in circular capillaries in the Taylor flow regime is investigated by using the volume-of-fluid method. The dynamics of formation and rise of Taylor bubbles in glass capillaries of 1, 0.5, 0.75, and 0.3 mm diameter for air−water and air−octane systems was simulated. The effects of superficial gas and liquid velocities, channel geometry (nozzle wall thickness, nozzle diameter, capillary diameter), wall adhesion (contact angle), and fluid properties (surface tension, viscosity) on the dynamics of bubble formation were investigated. The predicted bubble shapes and bubble formation periods were validated using the experimental data reported by Salman et al. (Salman, W.; Gavriilidis, A.; Angeli, P. Chem. Eng. Sci. 2006, 61, 6653−6666) for a wide range of experimental parameters. Such experimentally validated computational flow models will be useful to simulate the mass transfer and reactions in microcapillaries/channels. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800806f#cor1 [article] Numerical simulations of bubble formation and rise in microchannels [texte imprimé] / Deepak Goel, Auteur ; Vivek V. Buwa, Auteur . - 2009 . - pp. 8109–8120. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8109–8120 Mots-clés : Microchannels  Gas−liquid  flow  Bubbles Résumé : Gas−liquid flow in microchannels is of fundamental importance to many engineering applications involving microreactors, monolith reactors, microheat exchangers, and several other microfluidic devices. Slug flow, characterized by motion of long bubbles, also referred to as Taylor bubbles, is the most important of the different two-phase flow regimes observed in microchannels. In this work, the formation of bubbles and their rise in circular capillaries in the Taylor flow regime is investigated by using the volume-of-fluid method. The dynamics of formation and rise of Taylor bubbles in glass capillaries of 1, 0.5, 0.75, and 0.3 mm diameter for air−water and air−octane systems was simulated. The effects of superficial gas and liquid velocities, channel geometry (nozzle wall thickness, nozzle diameter, capillary diameter), wall adhesion (contact angle), and fluid properties (surface tension, viscosity) on the dynamics of bubble formation were investigated. The predicted bubble shapes and bubble formation periods were validated using the experimental data reported by Salman et al. (Salman, W.; Gavriilidis, A.; Angeli, P. Chem. Eng. Sci. 2006, 61, 6653−6666) for a wide range of experimental parameters. Such experimentally validated computational flow models will be useful to simulate the mass transfer and reactions in microcapillaries/channels. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800806f#cor1

Numerical simulations of liquid — liquid flows in microchannels / Richa Raj in Industrial & engineering chemistry research, Vol. 49 N° 21 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10606-10614 Titre : Numerical simulations of liquid — liquid flows in microchannels Type de document : texte imprimé Auteurs : Richa Raj, Auteur ; Nikita Mathur, Auteur ; Vivek V. Buwa, Auteur Année de publication : 2011 Article en page(s) : pp. 10606-10614 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Liquid  liquid  flow  Numerical  simulation Résumé : Liquid-liquid flows in microchannels are important to microreactors/microfluidic devices that are used to carry out liquid-liquid reactions, extractions, emulsifications, etc. In this work, we report numerical investigations of drop/slug formation and flow regimes for liquid-liquid (oil-water) flow in microchannels. The Volume of Fluid (VOF) method was used to simulate the dynamics of water drop/slug formation in silicon oil, and the predicted drop/slug shapes/lengths were compared with previous literature measurements [Garstecki et al., Lab Chip 2006, 6, 437-446]. The effects of flow rates of water and oil phases (0.019―0.417 and 0.004―0.14 μL/s, respectively), channel size, liquid-liquid distributor (T-junction and Y-junction), and liquid viscosity on liquid-liquid flow regimes and slug lengths were investigated. The predicted drop/slug formation dynamics/slug lengths agreed satisfactorily with the aforementioned Garstecki et al. literature measurements for Qwater/Qoil in the range of 0.1-1.7. However, for Qwater/Qoil > 1.7, unlike the (long) slug flow reported in the aforementioned Garstecki et al. literature, a parallel flow was observed in the numerical simulations. The effect of wall adhesion (contact angle) on the flow regimes and slug lengths was also investigated. The experimentally validated computational model will be useful to simulate mixing, transport processes, and chemical reactions in microchannels. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447953 [article] Numerical simulations of liquid — liquid flows in microchannels [texte imprimé] / Richa Raj, Auteur ; Nikita Mathur, Auteur ; Vivek V. Buwa, Auteur . - 2011 . - pp. 10606-10614. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10606-10614 Mots-clés : Liquid  liquid  flow  Numerical  simulation Résumé : Liquid-liquid flows in microchannels are important to microreactors/microfluidic devices that are used to carry out liquid-liquid reactions, extractions, emulsifications, etc. In this work, we report numerical investigations of drop/slug formation and flow regimes for liquid-liquid (oil-water) flow in microchannels. The Volume of Fluid (VOF) method was used to simulate the dynamics of water drop/slug formation in silicon oil, and the predicted drop/slug shapes/lengths were compared with previous literature measurements [Garstecki et al., Lab Chip 2006, 6, 437-446]. The effects of flow rates of water and oil phases (0.019―0.417 and 0.004―0.14 μL/s, respectively), channel size, liquid-liquid distributor (T-junction and Y-junction), and liquid viscosity on liquid-liquid flow regimes and slug lengths were investigated. The predicted drop/slug formation dynamics/slug lengths agreed satisfactorily with the aforementioned Garstecki et al. literature measurements for Qwater/Qoil in the range of 0.1-1.7. However, for Qwater/Qoil > 1.7, unlike the (long) slug flow reported in the aforementioned Garstecki et al. literature, a parallel flow was observed in the numerical simulations. The effect of wall adhesion (contact angle) on the flow regimes and slug lengths was also investigated. The experimentally validated computational model will be useful to simulate mixing, transport processes, and chemical reactions in microchannels. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447953