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Mixing of complex oral health products: experimental and computational fluid dynamics investigations

Cortada Garcia, Marti; (2018) Mixing of complex oral health products: experimental and computational fluid dynamics investigations. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The objective of this research is to provide insight into the mixing process of glycerol with a gel made of carbomer and Polyethylene glycol, which is a critical step in the manufacturing of non-aqueous toothpastes. Computational fluid dynamics (CFD) was used as a diagnostics tool, and experimental work was needed to validate the CFD models. First, the applicability of CFD was assessed in a simple stirred tank equipped with a Rushton turbine, and the computational model was validated against accurate experiments of power requirement for agitation obtained with the combination of an air bearing and a load cell. Then, a more geometrically similar mixing tank to the pilot plant scale mixer was built, and a CFD model was implemented to study the flow behaviour of two different mixtures of glycerol and the carbomer gel. The simulations indicated that the mixer prevents the formation of stagnant zones, the angular velocity component is notably greater than the other two components, and the velocity magnitude of the fluid decays fast away from the blades of the impeller. These simulations were validated with the particle image velocimetry (PIV) technique. The mixing time of different mixtures with passive tracers was studied using the previous CFD model, which was modified to include the transport of species equation. The simulation time was prohibitively long, and the alternative approach of studying the mixing time with a Lagrangian particle tracking method was also attempted. The mixing time was evaluated experimentally using the planar laser induced fluorescence (PLIF) technique. Finally, the mixing performance was assessed by means of the Poincaré maps and stretching fields.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Mixing of complex oral health products: experimental and computational fluid dynamics investigations
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2018. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
Keywords: Mixing, Computational Fluid Dynamics (CFD), Non-Newtonian fluids, PIV, PLIF, Power consumption, Toothpaste, GSK
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/10064475
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