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Title: Mixing of complex oral health products : experimental and computational fluid dynamics investigations
Author: Cortada Garcia, Marti
ISNI:       0000 0004 7660 0061
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2018
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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.
Supervisor: Angeli, P. ; Mazzei, L. ; Dore, V. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available