Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Rheo-NMR of complex fluids under startup, steady state and large amplitude oscillatory shear(Montana State University - Bozeman, College of Engineering, 2021) Jayaratne, Jayesha S.; Chairperson, Graduate Committee: Joseph D. Seymour and Sarah L. Codd (co-chair); This is a manuscript style paper that includes co-authored chapters.Fluids are categorized as either simple or complex based on the intricacy of their structure and material response to deformation. Simple fluids composed of small molecules subject to deformation, readily flow with linear interaction dynamics with neighboring molecules. In contrast complex fluids like polymers, micelle solutions, colloidal gels and suspensions, composed of larger molecules or particulates alter the dynamics of individual constituents during deformation, requiring complicated constitutive models. Complex fluids are encountered daily, as they are found in consumer products such as food, pharmaceutical and personal care products. Knowing flow characteristics of these consumer products and their raw materials under industrially applicable deformations enables engineers to design efficient industrial processes and to formulate products to desired qualities. While classical rheology (the study of the flow and deformation of matter) techniques give good estimation of stress-strain bulk flow response, it fails to provide local flow information. Proton nuclear magnetic resonance (1H-NMR) has been used to measure spatially and temporally resolved velocities of fluids subject to mechanical deformation. This research field is known as 'Rheo-NMR' and is a novel flow measuring technique in that it is non-invasive and able to quantify three-dimensional velocity fields even of opaque fluids. Velocity responses of complex fluids like worm-like micelle solutions, yield stress fluids and shear thinning fluids were studied under varied mechanisms of deformation and were compared to the responses of simple Newtonian fluids. How local velocities of the fluids change over time when a steady shear is applied suddenly, how the velocity fields are affected on applying large oscillatory shear deformations and how using different shearing geometries impacts the local flow response were explored. Using Rheo-NMR techniques, experimental protocols to study spatio-temporal velocity fields of complex fluids were developed and data analysis methods for quantifying such measurements were established.Item Magnetic resonance studies of fluid transport in porous systems and medical devices(Montana State University - Bozeman, College of Engineering, 2017) Nybo, Elmira; Chairperson, Graduate Committee: Sarah L. Codd; Joseph D. Seymour (co-chair)This research describes the application of nuclear magnetic resonance (NMR) techniques for non-invasive investigation of fluid transport and hydrodynamics in porous systems and medical devices. NMR microscopy is used to obtain information about internal structures and transport properties in porous materials and opaque systems. Controlling dispersion within restricted pore spaces is of importance in a variety of applications including soil consolidation and dewatering and electromigration of solutes. NMR pulsed gradient stimulated echo (PGSTE) techniques combined with electroosmotic flow (EOF) are used to study diffusion and dispersion coefficients in model glass bead packs. The results show that significant EOF-induced backflow can cause structural changes and alter the flow. Understanding the transport of liquids in porous materials during the application of electrical field holds promise for solving problems involving the delivery of binding agents to infill the pore space in rigid cement-based structures via electroosmosis. NMR PGSTE techniques and micro-CT scan imaging were used to study fluid transport and structural changes in a hydrating cement paste in a closed cell. It is shown that EOF in closed cement paste samples caused a significant increase in macroscopic void volume compared to closed samples with no flow. Needleless connectors (NCs) are commonly used medical devices with complicated internal design that leads to flow complexity that may cause undesirable bacterial deposition and biofilm formation. Magnetic resonance imaging (MRI) is applied to acquire spatial velocity maps of fluid flow at various positions within the devices. MRI velocimetry is demonstrated as an effective method to quantify flow patterns and fluid dynamic dependence on structural features of NCs. Alginate and alginate-based materials find an increasing interest in environmental engineering as adsorbents for heavy metal recovery from aqueous solutions. A Ca 2+ and Cu 2+ containing fluid flow through calcium-based alginate gel has been visualized using NMR velocimetry. NMR indicated velocity changes in gel capillaries caused by ion exchange processes and followed gel structural changes. NMR microscopy is shown as an effective method to describe fluid transport and internal structural features in opaque porous systems and medical devices.