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Characterising the non-ideal behaviour of a Carbopol gel flowing in thin conduits

University of British Columbia

This thesis examines three problems related to the slow flow of a viscoplastic fluid in a thin conduit in order to characterise unique effects of its complex rheology. The methodology is experimental and we use Carbopol exclusively as a model yield stress fluid. The first part of this thesis is dedicated to exploring the flow behaviour near obstructions in a thin slot. We find that the fore-aft symmetry which is expected theoretically to be broken. The asymmetry is robust, as demonstrated by varying the shape and number of the obstacles, the surfaces of the cell walls, and the steadiness of the flow rate. The results suggest that a rheological hysteresis near the yield point may be the cause of the asymmetry. The second part of this thesis demonstrates wall-slip behaviour in a fully developed Poiseuille flow. The simultaneous velocity and in-situ viscometry measurements are exploited to determine the kinematics and dynamics of the flow in a glass capillary. The slip velocity is related to the wall-shear stress, using a power-law scaling, with an exponent independent of the microstructure of the fluid and viscosity of the solvent. The third part of this thesis is dedicated to investigating the multi-layered flow of miscible liquids in a thin, horizontal channel with chemical reaction at the interface. The fluid layers are vertically stratified in the thickness direction and chemical reaction leads to gelation at the interface. A systematic study is performed to examine the hydrodynamic stability of the flow as well as the growth rate of the gel. Our observations suggest that the stability of flow configuration is sensitive to the slight inclination angle in case of fully-reacted flow, and confirm that the gel layer grows diffusively along the length of the cell.

Text

2020-02-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/73592

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/