Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injection
Mixing in a reactor can be achieved mechanically or by the injection of a gas. This can be done by injecting a gas towards the bottom of the tank. The induced flow recirculation and then the stirring quality depends on the bubbles morphology, rising velocity and frequency detachment. This study focu...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2023-11-01
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| Series: | Chemical Engineering Journal Advances |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2666821123000844 |
| _version_ | 1797388653759037440 |
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| author | Laurent Jossic Philippe Séchet Albert Magnin Ali Hojeij Stéphane Hattou |
| author_facet | Laurent Jossic Philippe Séchet Albert Magnin Ali Hojeij Stéphane Hattou |
| author_sort | Laurent Jossic |
| collection | DOAJ |
| description | Mixing in a reactor can be achieved mechanically or by the injection of a gas. This can be done by injecting a gas towards the bottom of the tank. The induced flow recirculation and then the stirring quality depends on the bubbles morphology, rising velocity and frequency detachment. This study focus on the case where the stirred fluid exhibits a yield stress. It is in line with previous studies on the gas cavity at the injection point [1], the induced flow recirculation [2] and the numerical simulation [3]. Here we quantified the bubbles diameters, aspect ratios and velocities as a function of the air flow rate, rheological parameters and tank size. Scaling laws and correlations based on the characteristic dimensionless numbers governing the flow have been proposed and validated experimentally. It was found that bubble frequencies and consequently bubble volumes and velocities are mainly governed by the balance between inertial and buoyancy forces. However, viscous and yield stress effects play an important role along buoyancy and inertial in defining the bubble aspect ratios. Weakly inertial flows are characterized by elongated bubbles while high inertial flows produce almost spherical bubbles. These experimental results are of practical interest for the design of reactor or digester where yield stress fluids have to be stirred. |
| first_indexed | 2024-03-08T22:43:54Z |
| format | Article |
| id | doaj.art-04b70ae45c5346619858f78b27242010 |
| institution | Directory Open Access Journal |
| issn | 2666-8211 |
| language | English |
| last_indexed | 2024-03-08T22:43:54Z |
| publishDate | 2023-11-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Chemical Engineering Journal Advances |
| spelling | doaj.art-04b70ae45c5346619858f78b272420102023-12-17T06:42:09ZengElsevierChemical Engineering Journal Advances2666-82112023-11-0116100527Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injectionLaurent Jossic0Philippe Séchet1Albert Magnin2Ali Hojeij3Stéphane Hattou4Corresponding author.; Laboratoire Rhéologie et Procédés, Université Grenoble Alpes, Grenoble INP, CNRS (UMR 5520), BP 53 Domaine Universitaire, Grenoble Cedex 9 38041, FranceLEGI, Université Grenoble Alpes, Grenoble INP, CNRS (UMR 5519), BP 53 Domaine Universitaire, Grenoble Cedex 9 38041, FranceLaboratoire Rhéologie et Procédés, Université Grenoble Alpes, Grenoble INP, CNRS (UMR 5520), BP 53 Domaine Universitaire, Grenoble Cedex 9 38041, FranceLaboratoire Rhéologie et Procédés, Université Grenoble Alpes, Grenoble INP, CNRS (UMR 5520), BP 53 Domaine Universitaire, Grenoble Cedex 9 38041, FranceArkolia Energies, Mudaison 34130, FranceMixing in a reactor can be achieved mechanically or by the injection of a gas. This can be done by injecting a gas towards the bottom of the tank. The induced flow recirculation and then the stirring quality depends on the bubbles morphology, rising velocity and frequency detachment. This study focus on the case where the stirred fluid exhibits a yield stress. It is in line with previous studies on the gas cavity at the injection point [1], the induced flow recirculation [2] and the numerical simulation [3]. Here we quantified the bubbles diameters, aspect ratios and velocities as a function of the air flow rate, rheological parameters and tank size. Scaling laws and correlations based on the characteristic dimensionless numbers governing the flow have been proposed and validated experimentally. It was found that bubble frequencies and consequently bubble volumes and velocities are mainly governed by the balance between inertial and buoyancy forces. However, viscous and yield stress effects play an important role along buoyancy and inertial in defining the bubble aspect ratios. Weakly inertial flows are characterized by elongated bubbles while high inertial flows produce almost spherical bubbles. These experimental results are of practical interest for the design of reactor or digester where yield stress fluids have to be stirred.http://www.sciencedirect.com/science/article/pii/S2666821123000844Yield stress fluidBubblesGas injectionStirring |
| spellingShingle | Laurent Jossic Philippe Séchet Albert Magnin Ali Hojeij Stéphane Hattou Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injection Chemical Engineering Journal Advances Yield stress fluid Bubbles Gas injection Stirring |
| title | Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injection |
| title_full | Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injection |
| title_fullStr | Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injection |
| title_full_unstemmed | Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injection |
| title_short | Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injection |
| title_sort | bubbles morphology frequency and rising velocity in yield stress fluid under downward gas injection |
| topic | Yield stress fluid Bubbles Gas injection Stirring |
| url | http://www.sciencedirect.com/science/article/pii/S2666821123000844 |
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