Persistence of vortical structures in dense suspensions and shear-thinning fluids: Characterization of vortex formation and evolution
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Authors
Barnes, Moira
Date
2024-04-30
Type
thesis
Language
eng
Keyword
Experimental fluid mechanics , Vortex dynamics , Ultrasound imaging , Non-Newtonian flows , Separated flows
Alternative Title
Abstract
The following thesis explores the formation and evolution of coherent vortical structures formed in dense suspensions and fluids with strong non-Newtonian shear-thinning behaviour. The work is motivated by the inherent complexity of cardiovascular flows, as blood is a dense suspension and a shear-thinning fluid. Flows typical of the human circulatory system exhibit a high degree of unsteadiness where the formation of coherent vortical structures occurs within confinement. This problem is studied experimentally using analogous fluids and flow configurations; examining first the effect of solid volume fraction on vortex-ring formation in dense suspensions and second, the effect of shear-thinning strength on vortex-ring formation and small-scale structure coalescence in pulsatile and steady flows. To enable these experiments, a Lagrangian ultrasound-based imaging technique was further developed, allowing path-dependent parameters such as entrainment in dense suspensions of up to 40\% volume fraction to be measured directly. Across the varied composition and parameterization of the different fluids and configurations studied, unifying observations are found, namely that unsteady large-scale roll-up of coherent vortical structures appears to generally persist with increasing volume fraction or shear-thinning strength in the early stages of formation. The findings presented in this thesis contribute to a deeper comprehension of how real blood properties influence vortex formation, particularly akin to those observed in the human heart. This knowledge helps inform indicators of cardiovascular health and aids in the design of heart valve replacements.
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Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
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Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 4.0 International
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 4.0 International