Dissertations / Theses on the topic 'Non-Newtonian fluid mechanics'
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Keiller, Robert A. "Non-Newtonian extensional flows." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315030.
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Gouldson, Iain William. "The flow of Newtonian and non-Newtonian fluids in an annular geometry." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243035.
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Mennad, Abed. "Singular behaviour of Non-Newtonian fluids." Thesis, Peninsula Technikon, 1999. http://hdl.handle.net/20.500.11838/1253.
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Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 1999Since 1996, a team at the Centre for Research in Applied Technology (CRATECH) at Peninsula Technikon, under NRF sponsorship and with industrial co-operation, has been involved in the simulation of Non-Newtonian flow behaviour in industrial processes, in particular, injection moulding of polymers. This study is an attempt to deal with some current issues of Non-Newtonian flow, in small areas, from the viewpoint of computational mechanics. It is concerned with the numerical simulation of Non-Newtonian fluid flows in mould cavities with re-entrant corners. The major complication that exists in this numerical simulation is the singularity of the stresses at the entry of the corner, which is responsible for nonintegrable stresses and the propagation of solution errors. First, the study focuses on the derivation of the equations of motion of the flow which leads to Navier- Stokes equations. Thereafter, the occurrence of singularities in the numerical solution of these equations is investigated. Singularities require special attention no matter what numerical method is used. In finite element analysis, local refinement around the singular point is often employed in order to improve the accuracy. However, the accuracy and the rate of convergence are not, in general, satisfactory. Incorporating the nature of singularity, obtained by an asymptotic analysis in the numerical solution, has proven to be a very effective way to improve the accuracy in the neighborhood of the singularity and, to speed up the rate of convergence. This idea has been successfully adopted in solving mainly fracture mechanics problems by a variety of methods: finite difference, finite elements, boundary and global elements, and spectral methods. In this thesis, the singular finite elements method (SFEM), similar in principle to the crack tip element used in fracture mechanics, is proposed to improve the solution accuracy in the vicinity of the singular point and to speed up the rate of convergence. This method requires minor modifications to standard finite element schemes. Unfortunately, this method could not be implemented in this study due to the difficulty in generating the mesh for the singular element. Only the standard finite element method with mesh refinement has been used. The results obtained are in accordance with what was expected.
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Van, Sittert Fritz Peter. "The effect of pipe roughness on non-Newtonian turbulent flow." Thesis, Cape Technikon, 1999. http://hdl.handle.net/20.500.11838/1035.
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Thesis (MTech (Civil Engineering))--Cape Technikon, Cape Town, 1999Pipe roughness is known to greatly increase the turbulent flow friction factor for Newtonian fluids. The well-known Moody diagram shows that an order of magnitude increase in the friction is possible due to the effect of pipe roughness. However, since the classical work of Nikuradse (1926 -1933), very little has been done in this area. In particular, the effects that pipe roughness might have on non-Newtonian turbulent flow head loss, has been all but totally ignored. This thesis is directed at helping to alleviate this problem. An experimental investigation has been implemented in order to quantify the effect that pipe roughness has on non-Newtonian turbulent flow head loss predictions. The Balanced Beam Tube Viscometer (BBTV), developed at the University of Cape Town, has been rebuilt and refined at the Cape Technikon and is being used for research in this field. The BBTV has been fitted with pipes of varying roughness. The roughness of smooth P\'C pipes was artificially altered using methods similar to those of Nikuradse. This has enabled the accumulation of flow data in laminar and turbulent flow in pipes that are both hydraulically smooth and rough Newtonian and non-Newtonian fluids have been used for the tests. The data have been subjected to analysis using various theories and scaling laws. The strengths and problems associated with each approach are discussed and It is concluded that roughness does have a significant effect on Newtonian as well as non-Newtonlan flow.
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Lockett, Timothy James. "Numerical simulation of inelastic non-Newtonian fluid flows in annuli." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/8422.
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Yim, Samson Sau Shun. "The effect of flow stability on residence time distribution of Newtonian and non-Newtonian liquids in couette flow." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264191.
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Goshawk, Jeffrey Alan. "Enhancement of the drainage of non-Newtonian liquid films by oscillation." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333685.
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Kabamba, Batthe Matanda. "Evaluation of centrifugal pump performance derating procedures for non-Newtonian slurries." Thesis, Cape Peninsula University of Technology, 2006. http://hdl.handle.net/20.500.11838/2170.
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Thesis (MTech(Civil Engineering))--Cape Peninsula University of Technology, 2006.The performance of a centrifugal pump is altered for slurry or viscous materials (Stepanoff, 1969) and this needs to be accounted for. Usually, the suitable selection and evaluation of centrifugal pumps is based only on water pump performance curves supplied by the pump manufacturer (Wilson, Addie, Sellgren & Clift, 1997). In 1984 Walker and Goulas conducted a number of pump performance tests with kaolin clay slurries and coal slurries on a Warman 4/3 AH horizontal slurry pump and a Hazleton 3-inch B CTL horizontal pump (Walker and Goulas, 1984). Walker and Goulas have analysed the test data and correlated the performance derating both at the best efficiency flow rate (BEP) and at 10% of the best efficiency flow rate (0.1 BEP) to the modified pump Reynolds number (NRep). They have noticed that the head and the efficiency reduction ratio decreased for the pump Reynolds number less then 10⁶. Furthermore, Walker and Goulas obtained a reasonably good agreement (± 5%) between pump test data for non-Newtonian materials and pump performance prediction using the Hydraulics Institute chart. Sery and Slatter (2002) have investigated pump deration for non-Newtonian yield pseudoplastic materials. The NRep was calculated using the Bingham plastic viscosity (µp). Results have shown good agreement with regard to head and efficiency reduction ratios in comparison with previous work. However, Sery and Slatter's pump performance correlation using the HI chart did not reach the same conclusion. Error margin of ± 20% and ± 10% were found for head and efficiency respectively. This study is an attempt to reconcile the differences between Walker and Goulas (1984) and Sery and Slatter (2002) and extend the evaluation of these derating methods to pseudoplastic materials. The test work was conducted in the Flow Process Research Centre laboratory of the Cape Peninsula University of Technology using two centrifugal pumps; a Warman 6/4 and a GrW 4/3. The materials used were water, CMC solution bentonite and kaolin suspension at different concentrations (7% and 9% by weight for bentonite; 5%, 6% and 7% by weight for CMC; 17%, 19% and 21% by volume for kaolin).
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Kheng, Tan Ka. "Gas diffusion into viscous and non-Newtonian liquids and the onset of convection." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321528.
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Thorvaldsen, Gary Sven. "The effect of the particle size distribution on non-Newtonian turbulent slurry flow in pipes." Thesis, Cape Technikon, 1996. http://hdl.handle.net/20.500.11838/896.
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Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town,1996The handling of solid-liquid suspensions is an important concern within the chemical and processing industries and many theoretical models have been proposed to try and explain and predict turbulent flow behaviour. However, the prediction of turbulent flow from only the viscous properties of non-Newtonian suspensions has over the years been questioned by researchers. This thesis considers theoretical models well established in the literature and the Slatter model, which uses both the rheology of the suspension and the particle size distribution of the solids. These models are used to analyze the experimental data and the effect that particle size and the particle size distribution has on turbulent flow behaviour. The literature concerning the rheological fundamentals relevant to fluid flow in pipes has been examined. The Newtonian turbulent flow model as well as the non-Newtonian models of Dodge & Metzner, Torrance, Kemblowski & Kolodziejski, Wilson & Thomas and Slatter have been reviewed. Test work was conducted at the University of Cape Town's Hydrotransport Research Laboratory using a pumped recirculating pipe test rig. The test apparatus has been fully described and calibration and test procedures to enable collecting of accurate pipeline data have been presented. Three slurries were used in test work namely kaolin clay, mixture I (kaolin clay and rock flour) and mixture 2 (kaolin clay, rock flour and sand) with ad,s particle size ranging from 24/Lm to 170/Lm. The yield pseudoplastic model has been used to model and predict the laminar flow of the suspensions that were tested and the meth9J adopted by Neill (1988) has been used to determine the rheological constants. The pipeline test results have been presented as pseudoshear diagrams together with the theoretical model lines providing a visual appraisal of the performance of each model. The Slatter model predicts the test data best with the other theoretical models that were considered tending to under predict the head loss. The reason the Slatter model performs better than the other theoretical models is because this model can account for the wall roughness and particle roughness effect. Evidence to support this statement has been presented. This thesis highlights the fact that the particle size distribution is a vitally important property of the suspension and that it does influence turbulent flow behaviour. It shows that turbulence modelling using the particle roughness effect (eg Slatter, 1994) is valid and can be adopted for non-Newtonian slurries. It is concluded that the particle size distribution must be used to determine the particle roughness effect and this effect must be incorporated in the turbulent flow analysis of non-Newtonian slurries.
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Redmon, Jessica. "Stochastic Bubble Formation and Behavior in Non-Newtonian Fluids." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case15602738261697.
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Ntamba, Ntamba Butteur Mulumba. "Non-Newtonian pressure loss and discharge coefficients for short square-edged orifices plates." Thesis, Cape Peninsula University of Technology, 2011. http://hdl.handle.net/20.500.11838/1252.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2011.Despite the extensive research work carried out on flow through short square-edged orifice plates over the last century (e.g. Johansen, 1930; Benedict, 1977; Alvi et al., 1978; Swamee, 2005; ESDU, 2007), gaps in the engineering data still exist for certain ranges of flow conditions and geometries. The majority of data available in the literature are for Newtonian fluids in the turbulent flow regime (ESDU, 2007). Insufficient data have been observed for the orifice with pipe diameter ratio, β = 0.2, in the laminar flow regime. There are no experimental data for β = 0.3 and 0.57. The objective of this thesis was to conduct wide-ranging experimental studies of the flow in orifice plates, which included those geometrical configurations, by measuring pressure loss coefficients and discharge coefficients across the orifice plates using both Newtonian fluids and non-Newtonian fluids in both laminar and turbulent flow regimes. The test work was conducted on the valve test rig at the Cape Peninsula University of Technology. Four classical circular short square-edged orifice plates having, β = 0.2, 0.3, 0.57 and 0.7, were tested. In addition, two generation 0 Von Koch orifice plates (Von Koch, 1904), with equivalent cross sectional area were also tested for β = 0.57. Water was used as Newtonian fluid to obtain turbulent regime data and also for calibration purposes to ensure measurement accuracy and carboxymethyl cellulose, bentonite and kaolin slurries were used at different concentrations to obtain laminar and transitional loss coefficient data. The hydraulic grade line method was used to evaluate pressure loss coefficients (Edwards et al., 1985), while the flange tap arrangement method was used to determine the discharge coefficients (ESDU, 2007). A tube viscometer with three different pipe diameters was used to obtain the rheological properties of the fluids. The results for each test are presented in the form of pressure loss coefficient (kor) and discharge coefficient (Cd) against pipe Reynolds number (Re)
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Hirn, Adrian [Verfasser], and Rolf [Akademischer Betreuer] Rannacher. "Finite Element Approximation of Problems in Non-Newtonian Fluid Mechanics / Adrian Hirn ; Betreuer: Rolf Rannacher." Heidelberg : Universitätsbibliothek Heidelberg, 2011. http://d-nb.info/1179784111/34.
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Burger, Johannes Hendrik. "Non-Newtonian open channel flow: the effect of shape." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/1296.
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Thesis submitted in fulfilment of the requirements for the degree
Doctor of Technology: Mechanical Engineering
in the
Faculty of Engineering
at the
Cape Peninsula University of Technology
2014Open channels, flumes or launders are used in the mining industry to transport slurries during processing and to disposal sites. Water plays a major part in the makeup of these slurries, its usage and availability is critical in countries where there are strict water usage management programs. The optimisation of flume design involves the maximisation of solids transport efficiency whilst, at the same time reduces water usage. The design of open channels is complex as it is dependent on both the slurry rheology and the channel shape. Very little has been reported in the literature for predicting non-Newtonian laminar flow in open channels of arbitrary cross-section. The only method available was that proposed by Kozicki and Tiu (1967, 1986). The shape factors they used were those evaluated from analytical solutions for flow of Newtonian fluids in open channels of the same cross-section. However, they carried out no experimental work to validate their model. Few experimental studies have been made on the effect of shape on non-Newtonian flow in open channels. Naik (1983) tested kaolin in water suspensions in a rectangular channel. Coussot (1994) provided some data for the flow of a Herschel-Bulkley fluid in rectangular and trapezoidal channels. Fitton (2007; 2008) obtained data for flow of three different non-Newtonian fluids (carboxymethylcellulose, carbopol and thickened tailings) in a semi-circular channel. A large experimental database for non-Newtonian flow in rectangular open channels was published by Haldenwang (2003) at the Flow Process Research Centre, Cape Peninsula University of Technology. Guang et al. (2011) performed Direct Numerical Simulations of turbulent flow of a yield- pseudoplastic fluid in a semi-circular channel. They compared their simulations with actual field measurements and found them to over-predict the flow velocity by approximately 40%. The source for this discrepancy was difficult to ascertain. A comprehensive database was compiled during this research of the flow of three non–Newtonian fluids in rectangular, trapezoidal, semi-circular and triangular channels. The flow of carboxymethylcellulose solutions and aqueous kaolin and bentonite suspensions was investigated in a 10 meter long flume at angles ranging from 1° to 5° from the horizontal plane. The effect of channel shape on the friction factor-Reynolds number relationship for laminar and turbulent open channel flow of these three fluids was investigated. New models for the prediction of laminar and turbulent flow of non-Newtonian fluids in open channels of different cross-sectional shapes are proposed. The new laminar and turbulent velocity models are compared with three previously-published velocity models for laminar flow and five previously-published velocity models for turbulent flow using average velocity as comparison criteria. For each channel shape, the laminar flow data can be described by a general relationship, f = K/Re where f is the Fanning friction factor and Re is the appropriate Haldenwang et al. (2002) Reynolds number. The K values were found to be 14.6 for triangular channels with a vertex angle of 90°, 16.2 for semi-circular channels, 16.4 for rectangular channels and 17.6 for trapezoidal channels with 60 degree sides. These K values were found to be in line with those reported by Straub et al. (1958) and Chow (1969) for open channel laminar flow of Newtonian fluids as opposed to the assumption made by Haldenwang et al. (2002; 2004) of using a constant value of 16 based on the pipe flow paradigm for all channel shapes. This new laminar model gave a closer fit to the laminar flow data than those from the three previously-published models. However, the presence of the yield stress still presents a problem, which makes the flow prediction in laminar flow for such fluids not very accurate. The investigation on non-Newtonian turbulent flow of the three fluids in the four different shaped open channels revealed that the data was described by the modified Blasius equation f = a Re b where a and b are constant values determined for each channel shape and Re is the Haldenwang et al. (2002) Reynolds number. Values of a and b for a rectangular channel were found to be 0.12 and -0.330, for a semi- circular channel 0.048 and -0.205, for a trapezoidal channel with 60° sides, 0.085 and -0.266 and for a triangular channel with vertex angle of 90°, 0.042 and -0.202. New laminar and turbulent velocity models were derived from using the new laminar f = K/Re and turbulent f = a Re b, friction factor-Reynolds number relationship. The laminar velocity model did not always give the best result, but the majority of the time it did, compared to the three previously published models. The new turbulent velocity model yielded the best results when compared to the five previously published models using average velocity as comparison criteria. The composite power law modelling procedure of Garcia et al. (2003) used for pipe flow predictions was extended to the present work on non-Newtonian flow in open channels of various cross-sections. The results show that the modelling technique used by Garcia et al. (2003) for pipe flow can be used to adequately predict flow in an open channel of a given cross-sectional shape provided that an appropriate Reynolds number is used to take into account the non-Newtonian behaviour of the test fluid. It was found that the results using the Haldenwang et al. (2002) Reynolds number yielded better results than those based on the adapted Metzner-Reed Reynolds number. The correlations and models developed and experimentally validated during this research can be used to further improve the design of rectangular, semi-circular, trapezoidal and triangular open channels to transport non-Newtonian fluids.
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Fu, An. "Numerical Investigation of Laminar Flow and Heat Transfer in Circular Duct with Twisted Tape Inserted for Non-Newtonian Fluid." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1461592760.
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Modekurti, Arvind. "Numerical Investigation of Fluid Flow and Heat Transfer for Non-Newtonian Fluids Flowing through Twisted Ducts with Elliptical Cross-sections." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504782280273333.
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Shu, Yupeng. "Numerical Solutions of Generalized Burgers' Equations for Some Incompressible Non-Newtonian Fluids." ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/2051.
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The author presents some generalized Burgers' equations for incompressible and isothermal flow of viscous non-Newtonian fluids based on the Cross model, the Carreau model, and the Power-Law model and some simple assumptions on the flows. The author numerically solves the traveling wave equations for the Cross model, the Carreau model, the Power-Law model by using industrial data. The author proves existence and uniqueness of solutions to the traveling wave equations of each of the three models. The author also provides numerical estimates of the shock thickness as well as maximum strain $\varepsilon_{11}$ for each of the fluids.
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Kabengele, Kantu. "Identification of flow patterns for coarse particles transported in a non-Newtonian carrier using electrical resistance tomography." Thesis, Cape Peninsula University of Technology, 2012. http://hdl.handle.net/20.500.11838/1247.
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A dissertation submitted to the Faculty of Engineering, Cape Peninsula University of Technology, Cape Town, in partial fulfilment of the requirements for the MTech Degree in Mechanical Engineering
2012Flow features provide considerable guidance for the rational selection of techniques to predict hydraulic behaviour and for suitable operating conditions for pipelines. Traditionally, water was used to transport coarse particles, and it was necessary to operate at velocities at which the flow was turbulent in order to avoid blockage. Consequently the friction losses were too high for economic operation. In addition, wear on pipes, fittings and pumps presented serious problems. Nowadays, it is well established that it is possible to operate at very high solids concentration in a heavy vehicle (carrier fluid). Similar solids throughputs may be achieved at very much lower velocities by operating in the laminar flow regime. This results not only in lower power requirement, but it also reduces wear and water consumption. In spite of these potential benefits, only a few studies dealing with the transport of coarse particles in heavy media have been reported. Since the distinction between different flow patterns is of paramount importance for modelling purposes, as equations are flow pattern dependent, and given the importance of avoiding excessive wear of pipes at low and high velocities, the present work was carried out in the context of dense or non-Newtonian carrier fluid. This project comprised analysis of existing data acquired at the Flow Process and Rheology Centre of the Cape Peninsula University of Technology. Kaolin in the range of 6% to 15% volumetric concentration was used as a carrier fluid and coarse material in the range of 10% to 30% volumetric concentration was simulated by silica sand ranging in size from 1 mm to 3 mm. For the purpose of this study flow patterns derived from resistance curves for various mixtures, particle concentrations, particle grading and flow conditions were compared with “concentration profiles” and images obtained from electrical resistance tomography (ERT). It appeared from this work that the sand concentration does not change the flow pattern but increases or reduces the pressure gradients depending on the case. The concentration of kaolin carrier can change the flow patterns from layered to homogeneous flow, inducing an increase in total pressure gradients as it increases. Flow patterns obtained from ERT compared reasonably well with those derived from pressure gradients profiles. The transition velocities from layered to heterogeneous flow obtained from both methods were similar, especially for low and moderate carrier concentrations. As the kaolin carrier concentration or as the sand concentration increased it became more difficult to distinguish the transition velocity between heterogeneous and layered flow. More work is still needed to improve the ERT instrument and its image reconstruction software.
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Kalombo, Jean-Jacques Ntambwe. "Centrifugal pump derating non-Newtonian slurries: analysis of the viscosity to be used in the hydraulic institute method." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/905.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2013Centrifugal pumps are the most commonly used pumps in slurry transport systems. The design of pumping systems dealing with liquids more viscous than water requires a reliable method of pump performance prediction for the pump selection. For Newtonian fluids, the Hydraulic Institute method is well established, but there is no generally accepted method for non-Newtonian fluids. Many authors have fallen back on using the Hydraulic Institute method for non-Newtonian fluids. This requires a constant viscosity while non-Newtonian fluid viscosity varies with the shear rate. The question arises: What viscosity should be used in this method for non-Newtonian fluids? Two approaches have been developed: the use of a Bingham plastic viscosity made by Walker and Goulas (1984) and the use of the apparent viscosity calculated using an “equivalent hydraulic pipe” diameter, designed by Pullum et al. (2007). Previous results obtained from these two approaches are not in agreement. Therefore, the aim of this study is to explore a suitable procedure to determine a representative non-Newtonian viscosity to be used in the Hydraulic Institute method to predict the pump performance. To achieve this goal, a set of data was experimentally obtained and the existing data were reused. Test work was conducted using the pump test rig in the Flow Process Research Centre at the Cape Peninsula University of Technology. A Warman 4/3 pump was tested, using four concentrations of kaolin suspension and three concentrations of CMC solution. Five pump speeds were chosen to run these tests: 1200, 1400, 1600, 1800, and 2000 rpm. An additional data set obtained by testing two submersible centrifugal pumps with eight concentrations of sludge, in Stockholm, Sweden, was also analysed. These sets of data were analysed firstly according to the Walker and Goulas (1984) approach and secondly according to the Pullum et al. (2007) approach. The use of the apparent viscosity led to the better pump head prediction. The results of this prediction were close to those obtained in the Pullum et al. (2007) work, and even better in some cases. On the other hand, the use of the Bingham plastic viscosity showed better pump efficiency prediction, although the Walker and Goulas (1984) efficiency prediction range was achieved only for one pump out of five. The apparent viscosity reflected the non-Newtonian behaviour but it could not represent alone the non-Newtonian viscosity because of the poor efficiency predictions and the sensitivity of the Pullum et al. (2007) approach to a change in viscosity. From the results of this work, it is advisable that the pump performance prediction be done using both apparent and Bingham plastic viscosity, the apparent viscosity for the head prediction and the Bingham plastic viscosity for the efficiency prediction.
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Rundora, Lazarus. "Laminar flow in a channel filled with saturated porous media." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1306.
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Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2013The flow of reactive viscous fluids in porous media presents a theoretically challenging problem and has a broad range of scientific, technological and engineering applications. Real life areas where such flow systems are encountered include drying of food, geothermal energy extraction, nuclear waste disposal, the flow of heat and fluid inside human organs, insulation of buildings, groundwater movement, oil and gas production, astrophysical plasmas, magnetohydrodynamic (MHD) pumps and generators, metal extraction and granulation of metals, aerospace and ship propulsion and automobile exhaust systems. The reactions within such flow systems are inherently exothermic. It is in this view that we carry out studies of thermal effects and thermal stability criteria for unsteady flows of reactive variable viscosity non-Newtonian fluids through saturated porous media. The study focuses on non-Newtonian fluids mainly because the majority of industrial fluids exhibit non-Newtonian character. Particular focus will be on fluids of the differential type exemplified by third grade fluid. Both analytical and numerical techniques were employed to solve the nonlinear partial differential equations that were derived from the conservation principles, namely the principles of conservation of mass, momentum and energy balance. Graphical representations were adopted in trying to explain the response of solutions to various flow parameter variations. In chapter 1 we defined important terms and expressions, laid down a summary of important applications, carried out literature survey, stated the statement of the problem, the aims and objectives of the study as well as an outline of the envisaged research methodology. Chapter 2 focuses on the derivations of the fundamental equations that derive the flow system. These are the continuity equation, the momentum equation and the energy equation. In chapter 3 we computationally investigated the unsteady flow of a reactive temperature dependent viscosity third grade fluid through a porous saturated medium with asymmetric convective boundary conditions. The response of velocity and temperature fields to each of the various flow parameters was analysed and interpreted. A transient increase in both the velocity and temperature profiles with an increase in the reaction strength, viscous heating and fluid viscosity parameter was observed. On the other hand, a transient decrease in the field properties was observed with increase in non-Newtonian character and the porous medium shape parameter. The reaction was noticed to blow-up if, depending on other flow parameters, the reaction strength is not carefully controlled.
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Jeng, D. Isaac. "A Three-dimensional Model of Poroviscous Aquifer Deformation." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29977.
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A mathematical model is developed for quantification of aquifer deformation due to ground-water withdrawal and, with some modifications, is potentially applicable to petroleum reservoirs. A porous medium saturated with water is conceptually treated in the model as a nonlinearly viscous fluid continuum. The model employs a new three-dimensional extension, made in this thesis, of Helm's poroviscosity as a constitutive law governing the stress-strain relation of material deformation and Gersevanov's generalization of Darcy's law for fluid flow in porous media. Relative to the classical linear poroelasticity, the proposed model provides a more realistic tool, yet with greater simplicity, in modeling and prediction of aquifer movement.
Based on laboratory consolidation tests conducted on clastic sedimentary materials, three phases of skeletal compaction are recognized. They are referred to as "instantaneous compression", "primary consolidation" and "secondary compression" according to Terzaghi and Biot's theory of poroelasticity. Among the three modes of consolidation, material behavior during the secondary compression phase has a nonlinear stress-strain relationship and is strongly time-dependent, exhibiting a phenomenon often known as "creep". In poroelasticity, the primary and secondary compressions have been conceptually considered as two separate physical processes that require two sets of material parameters to be evaluated. In contrast, the proposed poroviscosity model is a unified theory of time-dependent skeletal compression that realistically describes the physical phenomena of sediment compression as one single transient process.
As a general model, two sets of governing equations are formulated for Cartesian and cylindrical coordinates, respectively, and allow for mechanical anisotropy and the assumption of principal hydraulic directions. Further simplifications of the governing equations are formulated by assuming mechanical isotropy, irrotational deformation and mechanical axisymmetry, which are more suitable for field applications. Incremental forms of the governing equations are also provided.Ph. D.
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Sarma, Sreedhara. "Fluid Mechanics of High Speed Deformable Roll coating. An experimental and theoretical study of film thickness and stability in high speed deformable roll coating flow with Newtonian and non-Newtonian liquids." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14842.
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Sgreva, Nicolò Rubens. "Influence of the fluid structure and elasticity on motions in a yield-stress material - Implications for geological systems Interaction between a falling sphere and the structure of a non-Newtonian yield-stress fluid." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASJ002.
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Cette thèse étudie la transition solide/fluide dans les fluides à contrainte-seuil, en utilisant des expériences de laboratoire et des simulations numériques. Les résultats obtenus à partir de l’étude de mécanique des fluides sont ensuite appliqués à la dynamique des systèmes magmatiques. Les objectifs sont d’évaluer comment la transition dépend de la structure du fluide et de son élasticité, quels sont les ingrédients nécessaires pour décrire mathématiquement cette transition et le mouvement du fluide, et dans quelles conditions cette description n’est plus valide. Deux systèmes ont été choisis pour la simplicité de leur dynamique dans le cas Newtonien et leur pertinence pour les systèmes géologiques: (1) le mouvement d’une sphère solide, et (2) le développement des panaches thermiques. Dans le premier cas, on a caractérisé expérimentalement la chute libre d’une shère dans un mélange aqueux de gels superabsorbants. L’objectif est ici d’étudier l’influence de la taille des grains de gel qui constituent la structure du fluide sur la dynamique de l’intrusion sphérique. Dans le second cas, l’approche utilisée est numérique, avec des simulations combinant les effets viscoplastiques et viscoélastiques. Le rôle de l’élasticité sur la déformation du fluide est ainsi caractérisé. Les résultats sont ensuite appliqués aux réservoirs magmatiques dans la croûte terrestre, où sont examinés les phénomènes à petite échelle (le mouvement des bulles de gaz et des poches de liquide fondu dans la chambre magmatique) et à grande échelle (la remontée d’un diapir magmatique et la déformation de la croûte au dessus de la chambre magmatique)In this thesis, the solid/flowing transition in yield-stress fluids is investigated using laboratory experiments and numerical simulations. The results obtained from the fluid mechanics study are then applied to the dynamics of magmatic systems. The aims are to evaluate how the transition depends on the fluid structure and its elasticity, what ingredients are needed to describe mathematically this transition and fluid motion, and when this description will break down. Two systems have been chosen for the simplicity of their dynamics in Newtonian fluids and their relevance to geological systems: (1) the motion of a solid sphere, and (2) the development of thermal plumes. Case (1) regards the experimental work on the free-fall of a sphere through a mixture of water and superabsorbent gel grains. The aim here is to investigate the influence that the size of particles which build up the structure of the fluid has on the dynamics of a spherical intruder. Case (2) is instead approached through numerical simulations that combine viscoelasticity and viscoplasticity together. The role of elasticity on the overall deformation of the fluid is characterized. Results are afterwards applied to crustal magmatic reservoirs in which both small scale phenomena (such as the motion of bubbles and melt pockets) and larger scale phenomena (deformation on the top of an entire magmatic chamber) are examined
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Rocco, Stefano. "Some geological implications of the flow of clay-water mixtures." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270525.
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This thesis investigates three problems in the general area of environmental fluid mechanics. The first two problems are related to liquid or gas flow through clay-water suspensions, with relevance for the underground storage of radioactive waste and also for understanding the mechanism of eruption in mud volcanoes. The third problem centres on the different problem of mixing in a turbulent buoyant plume. First, the injection of gas and water from a central source into a two-dimensional layer of clay confined between two circular horizontal plates is investigated. This provides a model of the potential pressurisation and failure of the seal rock around a radioactive waste repository as may arise if gas is continuously generated in the repository. As the gas injection pressure is gradually increased the cell walls deform and the clay moves radially outwards. However, at a critical radius, the liquid-clay interface becomes unstable and a series of channels propagate through the clay. When one of the channels reaches the edge of the domain the gas escapes and the pressure is released. As a result, the domain relaxes by elastic deformation and the clay seals the channel. In this way, continuous fluid injection leads to episodic release of gas from the cell. The second problem concerns the flow of mud along a vertical conduit driven by the combined effect of reservoir pressure and buoyancy associated with the gas injected at the base of the conduit. This represents an analogue model of the eruption of a mud volcano, in which mud rises from a deep reservoir to the surface. I find that the pressure associated with the reservoir and any buoyancy force produced by the migration of gas from deep in the reservoir to the surface leads to a continuous eruption if the net pressure is greater than the yield stress of the clay. If the reservoir pressure falls during such an event, the eruption will eventually stop, once the pressure reaches a dynamic yield stress condition. Only later, if the reservoir pressure increases to the static yield stress of the clay will the eruption start again, and this can lead to a series of eruption cycles which depend on the non-Newtonian rheology of the clay. In contrast, if this pressure is smaller than the yield stress of the clay, a series of episodic gas burst events can occur until the conduit is cleared of mud. The third problem relates to the mixing in a turbulent buoyant plume. Through a series of new experiments and some complementary theoretical modelling I show that the mixing in a turbulent plume is strongly affected by the eddies and leads to significant longitudinal dispersion in the flow. The implications of the modelling for determining the residence time distribution of the fluid in the plume is discussed.
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Gholami, Mohammad. "Shear Induced Migration of Particles in a Yield Stress Fluid." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1502793185991791.
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Ghosh, Jayanto K. "Finite element simulation of non-Newtonian flow in the converging section of an extrusion die using a penalty function technique." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1172094913.
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Chilcott, Mark David. "Mechanics of non-Newtonian fluids." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329946.
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Nguyen, Trong Dai. "Influences des propriétés non-Newtoniennes sur un mélange de scalaire passif." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0084.
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Cette thèse présente une étude expérimentale du problème de mélange dans les fluides complexes, étude menée en partenariat avec l’entreprise Sanofi Pasteur. Le mélange est un acte des plus fréquents dans la vie courante et aussi dans l’activité industrielle. On trouve dans la littérature de nombreuses études s’intéressant aux cuves de mélange pour en améliorer les performances à partir d’observations faites à grande échelle. Par contre, à notre connaissance, il y a peu de recherche sur l’hydrodynamique du mélange dans les fluides complexes. Dans notre travail, on étudie des fluides non-Newtoniens formés de solutions diluées de polymères caractérisés par leurs propriétés rhéofluidifiante et viscoélastique. Il s’agit de solutions aqueuses de Polyacrylamide (PAA) ou de la gomme de Xanthan (XG). Afin d’identifier la différence de comportement avec les fluides Newtoniens, une étude expérimentale avec de l’eau est effectuée dans les mêmes conditions que celles pour les fluides non-Newtoniens. Cette étude a été menée, en premier, sur un modèle réduit d’une cuve de mélange de Sanofi Pasteur. Les résultats obtenus, non représentés dans ce mémoire de thèse, nous ont amenés à mettre en place une étude fondamentale de l’écoulement dans un mélangeur de géométrie plus simple. Il s’agit alors de pouvoir contrôler les conditions initiales et de s’affranchir des effets secondaires de l’agitation pour ne s’intéresser qu’au mélange. Pour cela, la géométrie retenue est celle d’un mélangeur en T avec deux entrées perpendiculaires. L’exploration en 2D des champs de vitesse et de concentration de scalaire dans cette jonction en T est assurée simultanément aux moyens des techniques optiques (PIV et PLIF). Les observations montrent un effet non négligeable sur l’hydrodynamique et le mélange lié à la présence de polymères dans l’écoulement. De plus, les résultats obtenus permettent de calculer la tension de Reynolds uv et les flux de masse vc et uc. Ils seront utilisés par la suite pour vérifier leur conformité avec le modèle k epsilon couramment utilisé dans l’industrieThis thesis presents an experimental study of the mixing in complex fluids which is conducted in partnership with Sanofi Pasteur. The mixture is one of the most common act in everyday life and also in industrial activities. We found in the literature many studies focusing on the mixing tanks with objective to improve performance based on observation of large scale. By cons, in our knowledge, there is few or no research on the hydrodynamics of a mixture in complex fluides. In our work, we study non-Newtonian fluids formed of diluted solution of polymer which characterized by their viscoelastic and shear thinning properties. We used in this study aqueous solutions of polyacrylamide (PAA) or xanthan gum (XG). To identify the difference in behavior with Newtonian fluid, an experimental study with water is carried out under the same conditions as those non-Newtonian fluids. At first, this study was on a reduced mixing tank of Sanofi Pasteur. The results, which not shown in this thesis, led us to develop a fundamental study of flow in a mixer with a simple geometry. The objective is to be able to control the initial conditions and to avoid the side effects of agitation to focus on the mixture. For this, we chose a mixer in a T shape with two perpendicular inputs. Exploring 2D velocity and scalar concentration fields in this T-junction is provided simultaneously of optical techniques (PIV and PLIF). Observations show a significant effect on the hydodynamic and mixture related to the presence of polymers in the flow. In addition, results are used to calculate the Reynolds stress uv and the scalar flux vc and uc. They will be used to check their compliance with the k epsilon model that commonly used in industry
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Ducharme, Réjean 1970. "Capillary flow of non-Newtonian fluids." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23392.
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The flow of a two-dimensional incompressible non-Newtonian fluid, showing a viscoelastic behavior, has been studied using the White-Metzner model with a phenomenological law for the viscosity, the Spriggs' truncated power-law model. Our goal was to determine if these models could generate the oscillating instabilities appearing in such fluids at very high driving force. We studied the effect of various quantities on the time-dependent numerical simulations and noticed that the mesh length was not very important for the accuracy of the results. However, the time constant modulus appearing in the White-Metzner model and the applied pressure were of paramount importance for the relaxation time of a disruptive flow.We thus showed that this model was effective only at low pressure and that without adding new aspects to the study of the flow, such as compressibility, we could not obtain any oscillating flow at high pressure. Despite this fact, exact steady-state solutions, as well as a time-dependant solution in the case of very small Reynolds number ($R to$ 0), have been given.
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Gallup, Benjamin H. (Benjamin Hodsdon) 1982. "High speed imaging of transient non-Newtonian fluid phenomena." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32815.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaf 51).
In this thesis, I investigate the utility of high speed imaging for gaining scientific insight into the nature of short-duration transient fluid phenomena, specifically applied to the Kaye effect. The Kaye effect, noted by A. Kaye in the March 9, 1963 issue of Nature, is the deflection and rebound of a free-falling non-Newtonian fluid stream incident on a pool of the same fluid. The effect was successfully reproduced using Suave[TM] shampoo, and imaged using the Phantom[TM] High Speed Video system. This task involved developing a knowledge of the photographic process as applied to high speed imaging, and of non-Newtonian fluid mechanics. No precisely reproducible method for producing rebounding streams was found, and behavior contrary to the existing body of observation were noted. In conclusion, areas that merited further investigation and potential variables of interest to future Kaye effect research are discussed.
by Benjamin H. Gallup.
S.B.
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Anderson, Brian. "Development of a non-Newtonian latching device." Thesis, Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3855.
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Etemad, Seyed Gholamreza. "Laminar heat transfer to viscous non-Newtonian fluids in non-circular ducts." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28736.
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A computational and experimental study was made of the steady developing laminar convective heat transfer to viscous non-Newtonian fluids described by the power law model flowing in straight channels of circular and several non-circular cross-sections. In the numerical study the governing conservation equations in three dimensions subject to suitable boundary conditions were solved after appropriate discretization, using the Galerkin finite element method. Fourteen different cross-sectional geometries were studied numerically. Effects of temperature-dependent apparent viscosity, viscous dissipation as well as Prandtl number were included in the model. The thermal boundary conditions tested were: uniform wall temperature and uniform wall heat flux on the entire duct surface. Predicted velocity fields, pressure drop, and heat transfer distributions were compared with available data and simulation results as appropriate. Results are presented on the comparative thermal performance of various cross-sectional ducts.In the experimental study the critical Reynolds numbers were measured for distilled water flowing through a semi-circular and an equilateral triangular duct. Local Nusselt number distributions are presented for ducts with the horizontal bottom plane sides subjected to uniform heat flux while the rest of the channel is well insulated. The measured pressure drop and Nusselt number distribution for Carbopol solutions compared very well with the numerical predictions.
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Tonkin, Ruth Julie Jane. "Swirling pipeflow of non-Newtonian and particle-laden fluids." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/11673/.
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This thesis describes the application of novel swirl inducing pipe to various pipe configurations, when pumping a range of fluids and fluid / particle mixtures. An extensive experimental programme, incorporating particle image velocimetry and photography, was implemented using a pipe flow loop designed specifically for the purpose. Experimental data was obtained on the effect of a 4-lobe near-optimal swirl pipe on coal-water, sand-water and magnetite-water slurries of various particle size. Results indicated that swirl induction produced greater benefit for denser slurries and higher concentrations, and that swirl induced into slurries containing larger and denser particles decayed more rapidly. At low velocity, experimental data highlighted a reduction in the total pressure drop experienced across a 3.0m horizontal pipe section, a downward sloping section and vertical pipe bends, when the swirl-inducing pipe was present. PIV was used to measure the axial and tangential velocity of swirling flows downstream of a near-optimal swirl-inducing pipe. It was confirmed that a significant tangential velocity was generated when pumping water in the turbulent regime, however, when the fluid viscosity was increased, leading to laminar flow, no significant tangential velocity was detected.
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Dawson, Matthew A. (Matthew Aaron) 1983. "Modeling the dynamic response of low-density, reticulated, elastomeric foam impregnated with Newtonian and non-Newtonian fluids." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44750.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references.
Engineering cellular solids, such as honeycombs and foams, are widely used in applications ranging from thermal insulation to energy absorption. Natural cellular materials, such as wood, have been used in structures for millennia. However, despite their extensive use, a comprehensive understanding of the dynamic interaction between the interstitial fluid in the cells of the foam and the foam itself has yet to be developed. In this thesis, we explore the dynamic, compressive response of low-density, reticulated, elastomeric foam impregnated with Newtonian and non-Newtonian fluids. To develop tractable analytical models for this complex, non-linear phenomenon, a study is first undertaken on the permeability of foam under deformation. Using these results, a model is developed for the dynamic, uniaxial compressive response of low-density, reticulated, elastomeric foam filled with a viscous Newtonian fluid. This comprehensive model is found to be well approximated by a simpler model, based on the lubrication approximation. Furthermore, in the lubrication limit, a model for the dynamic, uniaxial compressive response of foam filled with a non-Newtonian fluid is also developed. All of the models presented in this thesis are supported by extensive experimental studies. The experiments also suggest that these models are applicable over a wide-range of parameters, such as strain, strain rate, and pore size. Finally, these models are used in two case studies to assess the feasibility of composite structures containing a layer of liquid-filled foam in dynamic loading applications. The first case study focuses on applications in energy absorption with the experimental design of a motorcycle helmet. The second case study focuses on applications in mitigating the effects of blast waves with a parametric study of the design of a blast wall.
(cont.) These studies provide insight into the usefulness of the models and demonstrate that composite structures with a layer of liquid-filled foam have enormous potential in a wide range of dynamic loading applications.
by Matthew A. Dawson.
Ph.D.
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Khosravi, Rahmani Ramin. "THREE-DIMENSIONAL NUMERICAL SIMULATION AND PERFORMANCE STUDY OF AN INDUSTRIAL HELICAL STATIC MIXER." See Full Text at OhioLINK ETD Center (Requires Adobe Acrobat Reader for viewing), 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1103149825.
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Dissertation (Ph.D.)--University of Toledo, 2004.Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 323-340.
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Matton, Yves S. M. Massachusetts Institute of Technology. "Use of low-density, reticulated, elastomeric foam impregnated with Newtonian and non-Newtonian fluids to design an impact absorption material." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65310.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 259-268).
The development of new threats in recent conflicts, such as improvised explosive devices (IEDs), requires the development of improved protection for US soldiers. The development of improved materials for helmets, in particular, is motivated by the social and economic costs of head injury. A versatile liner, adaptable to different types of helmets, with different constraints, would be useful. In this thesis, we first review the statistics related to head injuries from motor vehicle and recreational accidents and then describe the state of the art of current helmet design. An experimental study of the response of a widely used helmet liner material (polystyrene foam) and a new potential liner material (low-density, reticulated, elastomeric foam impregnated with Newtonian and non-Newtonian fluids) under impact shows some complementarities and leads to the concept of a composite material that would take advantage of the properties of the two materials. To conduct an extensive design analysis, comprehensive models are developed to model the behavior of each material under a wide range of impact energies. A complete model for the composite bilayer of the two materials is then compared to experimental data; the model gives a good description of the data. Using these results, three case studies are developed for a motorcycle helmet, a football helmet and a military helmet. The three case studies show a variety of constraints in term of thickness of the liner and impacting energies. Simulations are conducted using the models developed to indentify potential designs that would meet the requirement in term of peak linear acceleration (PLA) and in term of the specific constraints of each type of helmet. Finally, in an experimental study, some of the proposed designs are tested for repeated loading. The proposed designs enhance the level of protection in term of peak linear acceleration and show promising behavior under repeated impact testing.
by Yves Matton.
S.M.
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Kiani, Niloufar. "Nozzle Flow Study and Geometry Optimization of Shear Thinning Non-Newtonian Fluid, Fuel Tank Sealant." Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10838460.
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Applications of sealant and adhesive technologies in aerospace industries require appropriate and reliable sealing materials and tools to provide suitable sealing. Due to a growing use of integral fuel tanks, which utilize the aircraft structure for fuel containment, this study focuses on nozzle geometry optimization of aircraft fuel tank sealant in order to develop and facilitate sealant approval process and to ensure the implementation of suitable fuel tank sealing.
Computational Fluid Dynamics (CFD) analyses were performed to study the sealant flow characterization and behavior using Star-CCM+ software. An empirical model was developed by the aid of Design of Experiments (DOE) techniques in order to develop a reliable mathematical model based on the collected data from numerical results. Scanning Electron Microscopy (SEM) was utilized to investigate the fracture/deformation of hollow glass microballoons and entrapped air bubbles within the cured sealant.
The results of this research concluded that the bent in nozzle geometry increases the sealant pressure drop throughout the nozzle. There is an optimized value for travel distance and cross sectional dimension and geometrical shape within the nozzle geometry that minimizes overall dynamic viscosity of the sealant.
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Aggarwal, Nishith. "Computational viscoelastic drop dynamics and rheology." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 122 p, 2008. http://proquest.umi.com/pqdweb?did=1456285651&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Hariharan, Prasanna. "Peristaltic Pressure-Flow Relationship of Non-Newtonian Fluids in Distensible Tubes with Limiting Wave Forms." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123687109.
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Chakraborty, Symphony. "Dynamics and stability of a non-Newtonian falling film." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00828305.
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On étudie la dynamique d'un film mince d'un fluide non-newtonien s'écoulant sur un plan incliné sous l'action de la gravité en tenant compte des effets d'une rhéologie complexe sur la dynamique des ondes de surface. Au chapitre 3, les propriétés des ondes solitaires, qui organisent la dynamique désordonnée d'un film Newtonien, sont considérées. Des simulations numériques directes (DNSs) d'ondes solitaires ont été effectués et comparés aux résultats d'un modèle à quatre équations formulé dans [112]. Au chapitre 5, l'évolution d'un film de fluide en loi de puissance film est modélisée au moyen de l'approche aux résidus pondérés. Les comparaisons avec l'analyse de stabilité d'Orr-Sommerfeld et de la DNS est en bon accord dans les régimes linéaires et non linéaires. Un film de fluide viscoplastique est modélisé par la loi Herschel et Bulkley est étudié au chapitre 6. L'élasticité du pseudo-bouchon à l'interface est pris en compte par une relation constitutive élastovisco-plastique proposée par Saramito [121]. Un modèle est formulé en termes de quatre équations pour l'épaisseur du film, le débit local et les amplitudes des contraintes normales et tangentielles. Une analyse de stabilité linéaire donne des valeurs du nombre de Reynolds critique en bon accord avec l'analyse d'Orr-Sommerfeld.
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Biswas, Dipankar. "Transition to Turbulence in Non-Newtonian Fluids: An In-Vitro Study Using Pulsed Doppler Ultrasound for Biological Flows." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1417785253.
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Mitishita, Rodrigo Seiji. "Avaliação experimental da transmissão de pressão em tubulações preenchidas por fluidos viscoplásticos." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2598.
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CAPES; PetrobrasFluidos de perfuração apresentam comportamento viscoplástico, que é definido por uma tensão limite de escoamento. Se a tensão imposta não supera a tensão limite de escoamento, o material se comporta como um sólido elástico, e quando esta tensão é excedida, o fluido escoa como um líquido viscoso. Durante o processo de perfuração de poços de petróleo, válvulas posicionadas na extremidade da coluna de perfuração são atuadas por diferenças de pressão no fluido. Argumenta-se, entretanto, que pressões aplicadas na superfície não são totalmente transmitidas até a válvula, impedindo sua operação. Logo, a transmissão de pressão em fluidos viscoplásticos demanda mais estudo. Para suprir a falta de estudos experimentais sobre o assunto, uma avaliação experimental da transmissão de pressão em um fluido viscoplástico é realizada neste trabalho. O aparato experimental construído para este propósito consiste de uma longa tubulação em formato helicoidal (serpentina) mantida sob temperatura controlada, ao longo da qual estão instalados transdutores de pressão relativa. O fluido é bombeado a uma vazão controlada por uma bomba do tipo helicoidal. Durante os testes, o fluido de trabalho é pressurizado na serpentina até um certo patamar ao mesmo tempo em que as pressões são medidas. Os resultados dos testes com fluidos viscoplásticos corroboram a literatura, que afirma que um fluido com tensão limite de escoamento confinado em uma tubulação fechada não transmite totalmente a pressão imposta na entrada ao longo do restante da tubulação. Além disso, foi observado que a diferença de pressão entre dois pontos da tubulação quando o fluido está em repouso é proporcional à tensão limite de escoamento deste fluido. Os resultados experimentais foram comparados com resultados de simulações numéricas de dois modelos matemáticos desenvolvidos no Centro de Pesquisas em Reologia e Fluidos Não newtonianos (CERNN), com boa concordância.
Drilling fluids exhibit a viscoplastic behavior, which is defined by a yield stress. If the stress imposed to the fluid does not surpass the yield stress, the material behaves like an elastic solid; if the yield stress is exceeded, it flows like a viscous liquid. In well drilling operations, some valves installed on the drillpipe near the bottom of the hole are actuated by pressure differences in the drilling fluid. However, it has been argued that the pressure applied at the surface is not fully transmitted to the valve’s position, preventing its actuation. Therefore, the pressure transmission in viscoplastic fluids demands further investigation. In order to compensate for the lack of experimental studies about the problem, an experimental analysis of the pressure transmission in yield stress fluids has been performed in this work. The experimental rig consists of a long thermally-controlled helical pipe, on which are installed relative pressure transducers. Fluid is displaced by a helical pump at a controlled flow rate. During the experiments, the fluid is pressurized inside the closed pipeline while the pressures are measured and recorded. The results showed that, in agreement with literature, the pressure at one end of a closed pipeline filled with a yield stress fluid is not fully transmitted to the other end. Moreover, it was observed that the pressure gradient in the pressurized fluid is proportional to its yield stress, which indicates a relation between pressure transmission and the presence and magnitude of the yield stress. The experiments were compared to simulation work developed at the Research Center for Rheology and Non-Newtonian Fluids with good agreement.
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Casey, David Michael. "Characterization of Transition to Turbulence for Blood in an Eccentric Stenosis Under Steady Flow Conditions." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1418066674.
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Lashgari, Iman. "Global stability analysis of complex fluids." Licentiate thesis, KTH, Mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-139405.
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The main focus of this work is on the non-Newtonian effects on the inertial instabilities in shear flows. Both inelastic (Carreau) and elastic models (Oldroyd-B and FENE-P) have been employed to examine the main features of the non-Newtonian fluids; shear-thinning, shear-thickening and elasticity. Several classical configurations have been considered; flow past a circular cylinder, in a lid-driven cavity and in a channel. We have used a wide range of tools for linear stability analysis, modal, non-modal, energy and sensitivity analysis, to determine the instability mechanisms of the non-Newtonian flows and compare them with those of the Newtonian flows. Direct numerical simulations have been also used to prove the results obtained by the linear stability analysis. Significant modifications/alterations in the instability of the different flows have been observed under the action of the non-Newtonian effects. In general, shear-thinning/shear-thickening effects destabilize/stabilize the flow around the cylinder and in a lid driven cavity. Viscoelastic effects both stabilize and destabilize the channel flow depending on the ratio between the viscoelastic and flow time scales. The instability mechanism is just slightly modified in the cylinder flow whereas new instability mechanisms arise in the lid-driven cavity flow. We observe that the non-Newtonian effect can alter the inertial flow at both baseflow and perturbation level (e.g. Carreau fluid past a cylinder or in a lid driven cavity) or it may just affect the perturbations (e.g. Oldroyd-B fluid in channel). In all the flow cases studied, the modifications in the instability dynamics are shown to be strongly connected to the contribution of the different terms in the perturbation kinetic energy budget.QC 20140113
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Lavarda, Jairo Vinícius. "Convecção natural de fluidos de lei de potência e de Bingham em cavidade fechada preenchida com meio heterogêneo." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1306.
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CAPESVários estudos numéricos investigaram cavidades fechadas sob o efeito da convecção natural preenchidas com fluidos newtonianos generalizados (FNG) nos últimos anos pelas aplicações diretas em trocadores de calor compactos, no resfriamento de sistemas eletrônicos e na engenharia de polímeros. Neste trabalho é realizada a investigação numérica do processo de convecção natural de fluidos de lei de Potência e de Bingham em cavidades fechadas, aquecidas lateralmente e preenchidas com meios heterogêneos e bloco centrado. O meio heterogêneo é constituído de blocos sólidos, quadrados, desconectados e condutores de calor. Como parâmetros são utilizados a faixa de Rayleigh de 104 à 107, índice de potência n de 0, 6 à 1, 6, número de Bingham de 0, 5 até Bimax , sendo investigado da influência do número de Prandtl para cada modelo de fluido. Nas cavidades com meio heterogêneo são utilizadas as quantidades de blocos de 9, 16, 36 e 64, mantendo-se a razão entre a condutividade térmica do sólido e do fluido κ = 1. Para as cavidades com bloco centrado, são utilizados os tamanhos adimensionais de 0, 1 à 0, 9 com κ = 0, 1; 1 e 10. A modelagem matemática é realizada pelas equações de balanço de massa, de quantidade de movimento e de energia. As simulações são conduzidas no programa comercial ANSYS FLUENT R . Inicialmente são resolvidos problemas com fluidos newtonianos em cavidade limpa, seguida de cavidade preenchida com meio heterogêneo e posteriormente bloco centrado para validação da metodologia de solução. Na segunda etapa é realizada o estudo com os modelos de fluidos de lei de Potência e de Bingham seguindo a mesma sequência. Os resultados são apresentados na forma de linhas de corrente, isotermas e pelo número de Nusselt médio na parede quente. De maneira geral, a transferência de calor na cavidade é regida pelo número de Rayleigh, tamanho e condutividade térmica dos blocos, pelo índice de potência para o modelo de lei de Potência e do número de Bingham para o modelo de Bingham. O número de Prandtl tem grande influência nos dois modelos de fluidos. O meio heterogêneo reduz a transferência de calor na cavidade quando interfere na camada limite térmica para ambos os fluidos, sendo feita uma previsão analítica para o fluido de lei de Potência. Para bloco centrado, a interferência na camada limite com fluido de lei de Potência também foi prevista analiticamente. A transferência de calor aumentou com bloco de baixa condutividade térmica e pouca interferência e com bloco de alta condutividade térmica e grande interferência, para ambos os fluidos.
Many studies have been carried out in square enclosures with generalized Newtonian fluids with natural convection in past few years for directly applications in compact heat exchangers, cooling of electronics systems and polymeric engineering. The natural convection in square enclosures with differently heated sidewalls, filled with power-law and Bingham fluids in addition with heterogeneous medium and centered block are analyzed in this study. The heterogeneous medium are solid, square, disconnected and conducting blocks. The parameters used are the Rayleigh number in the range 104 - 107 , power index n range of 0, 6 - 1, 6, Bingham number range of 0, 5 - Bimax , being the influence of Prandtl number investigated for each fluid model. The number of blocks for heterogeneous medium are 9, 16, 36 and 64, keeping constant solid to fluid conductive ratio, κ = 1. For enclosures with centered block are used the nondimensional block size from 0, 1 to 0, 9, with solid to fluid conductive ratio in range κ = 0, 1; 1 and 10. Mathematical modeling is done by mass, momentum and energy balance equations. The solution of equations have been numerically solved in ANSYS FLUENT R software. Firstly, numerical solutions for validation with Newtonian fluids in clean enclosures are conducted, followed by enclosures with heterogeneous medium and centered block. Subsequently, numerical solutions of power-law and Bingham fluids with same enclosures configurations are conducted. The results are reported in the form of streamlines, isotherms and average Nusselt number at hot wall. In general, the heat transfer process in enclosure is governed by Rayleigh number, size and thermal conductivity of the blocks, power index n for power-law fluid and Bingham number for Bingham fluid. Both fluid models are very sensitive with Prandtl number changes. Heterogeneous medium decrease heat transfer in enclosure when affects thermal boundary layer for both fluid models. One analytical prediction was made for power-law fluid. An increase in heat transfer occurs with low thermal conductivity block and few interference and with high thermal conductivity block and great interference, for both fluids.
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Peterson, Emily Cassidy. "Shear-induced microstructure in hollow fiber membrane dopes." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50245.
Full textAbstract:
Hollow fiber membranes offer the opportunity to dramatically reduce the energy required to perform gas separations in the chemical industry. The membranes are fabricated from highly non-Newtonian precursor materials, including concentrated polymer solutions that sometimes also contain dispersed particles. These materials are susceptible to shear-induced microstructural changes during processing, which can affect the characteristics of the resulting membrane. This thesis explores several shear-related effects using materials and flow conditions that are relevant for fiber spinning. The findings are discussed as they relate to membrane processing, and also from the standpoint of enhancing our fundamental understanding of the underlying phenomena.
First, the effect of shear on polymeric dope solutions was investigated. Shear-induced demixing—a phenomenon not previously studied in membrane materials—was found to occur in membrane dopes. Phase separation experiments also showed that shear-induced demixing promotes macrovoid formation. The demixing process was found to depend not only on the instantaneous shear conditions, but also on the shear history of the solution. This suggests that low-shear flow processes that occur in the upstream tubing and channels used for fiber spinning can affect macrovoid formation.
The effect of viscoelastic media on dispersed particles was also explored. Shear-small-angle light scattering results showed that particles suspended in membrane dope solutions formed aggregated, vorticity-oriented structures when shear rates in the shear-thinning regime of the polymer solution were applied. Shear rates well below the shear-thinning regime did not produce any structure. In fact, the application of a Newtonian shear rate to a sample already containing the vorticity structure caused the sample to return to isotropy. Measurements using a highly elastic, constant-viscosity Boger fluid showed that strong normal forces alone are not sufficient to form the vorticity structures, but that shear thinning is also required.
Lastly, a study was conducted examining cross-stream migration of particles dispersed in viscoelastic media. Fluids exhibiting varying degrees of shear thinning and normal forces were found to have different effects on the particle distribution along the shear gradient axis in Poiseuille flow. Shear thinning was found to promote migration toward the channel center, while normal stresses tended to cause migration toward the channel walls.
In addition to hollow fiber spinning, many other industrially relevant applications involve polymer solutions and suspensions of particles in viscoelastic media. Often, the properties and performance of the material depend strongly on the internal microstructure. The results from the research described in this thesis can be used to guide the design of materials and processing conditions, so that the desired microstructural characteristics can be achieved.
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Das, Suma Rani. "Investigation of Design and Operating Parameters in Partially-Filled Rubber Mixing Simulations." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1479151141596147.
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Carrim, Abdul Hamid. "Group invariant solutions for the unsteady magnetohydrodynamic flow of a fourth grade fluid in a porous medium." Thesis, 2014. http://hdl.handle.net/10539/14929.
Full textAbstract:
The e ects of non-Newtonian uids are investigated by means of two appropri-
ate models studying a third and fourth grade uid respectively. The geometry
of both these models is described by the unsteady unidirectional
ow of an in-compressible
uid over an in nite at rigid plate within a porous medium. The uid is electrically conducting in the presence of a uniform applied magnetic eld that occurs in the normal direction to the ow.
The classical Lie symmetry approach is undertaken in order to construct
group invariant solutions to the governing higher-order non-linear partial dif-ferential equations. A three-dimensional Lie algebra is acquired for both uid ow problems.
In each case, the invariant solution corresponding to the non-travelling wave
type is considered to be the most signi cant solution for the uid ow model
under investigation since it directly incorporates the magnetic eld term. A numerical solution to the governing partial di erential equation is produced and a comparison is made with the results obtained from the analytical ap-proach.
Finally, a graphical analysis is carried out with the purpose of observing the
e ects of the emerging physical parameters. In particular, a study is carried
out to examine the in uences of the magnetic eld parameter and the non-Newtonian
fluid parameters.
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Aziz, Taha. "Group theoretical and compatibility approaches to some nonlinear PDEs arising in the study of non-Newtonian fluid mechanics." Thesis, 2015. http://hdl.handle.net/10539/17646.
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A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2015.This thesis is primarily concerned with the analysis of some nonlinear problems arising in the study of non-Newtonian fluid mechanics by employing group theoretic and compatibility approaches. It is well known now that many manufacturing processes in industry involve non-Newtonian fluids. Examples of such fluids include polymer solutions and melts, paints, blood, ketchup, pharmaceuticals and many others. The mathematical and physical behaviour of non-Newtonian fluids is intermediate between that of purely viscous fluid and that of a perfectly elastic solid. These fluids cannot be described by the classical Navier–Stokes theory. Striking manifestations of non-Newtonian fluids have been observed experimentally such as the Weissenberg or rod-climbing effect, extrudate swell or vortex growth in a contraction flow. Due to diverse physical structure of non-Newtonian fluids, many constitutive equations have been developed mainly under the classification of differential type, rate type and integral type. Amongst the many non-Newtonian fluid models, the fluids of differential type have received much attention in order to explain features such as normal stress effects, rod climbing, shear thinning and shear thickening. Most physical phenomena dealing with the study of non-Newtonian fluids are modelled in the form of nonlinear partial differential equations (PDEs). It is easier to solve a linear problem due to its extensive study as well due to
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(5929685), Vishrut Garg. "Dynamics of Thin Films near Singularities under the Influence of non-Newtonian Rheology." Thesis, 2019.
Find full textAbstract:
Free surface flows where the shape of the interface separating two fluids is unknown apriori are an important area of interest in fluid dynamics. The study of free surface flows such as the breakup and coalescence of drops, and thinning and rupture of films lends itself to a diverse range of industrial applications, such as inkjet printing, crop spraying, foam and emulsion stability, and nanolithography, and helps develop an understanding of natural phenomena such as sea spray generation in oceans, or the dynamics of tear films in our eyes. In free surface flows, singularities are commonly observed in nite time, such as when the radius of a thread goes to zero upon pinchoff or when the thickness of a film becomes zero upon rupture. Dynamics in the vicinity of singularities usually lack a length scale and exhibit self-similarity. In such cases, universal scaling laws that govern the temporal behavior of measurable physical quantities such as the thickness of a lm can be determined from asymptotic analysis and veried by high-resolution experiments and numerical simulations. These scaling laws provide deep insight into the underlying physics, and help delineate the regions of parameter space in which certain forces are dominant, while others are negligible. While the majority of previous works on singularities in free-surface flows deal with Newtonian fluids, many fluids in daily use and industry exhibit non-Newtonian rheology, such as polymer-laden, emulsion, foam, and suspension flows.
The primary goal of this thesis is to investigate the thinning and rupture of thin films of non-Newtonian fluids exhibiting deformation-rate-thinning (power-law) rheology due to attractive intermolecular van der Waals forces. This is accomplished by means of intermediate asymptotic analysis and numerical simulations which utilize a robust Arbitrary Eulerian-Lagrangian (ALE) method that employs the Galerkin/Finite-Element Method for spatial discretization. For thinning of sheets of power-law fluids, a signicant finding is the discovery of a previously undiscovered scaling regime where capillary, viscous and van der Waals forces due to attraction between the surfaces of the sheet, are in balance. For thinning of supported thin films, the breakdown of the lubrication approximation used almost exclusively in the past to study such systems, is shown to occur for films of power-law fluids through theory and conrmed by two dimensional simulations. The universality of scaling laws determined for rupture of supported films is shown by studying the impact of a bubble immersed in a power-law fluid with a solid wall.
Emulsions, which are ne dispersions of drops of one liquid in another immiscible liquid, are commonly encountered in a variety of industries such as food, oil and gas, pharmaceuticals, and chemicals. Stability over a specied time frame is desirable in some applications, such as the shelf life of food products, while rapid separation into its constituent phases is required in others, such as when separating out brine from crude oil. The timescale over which coalescence of two drops of the dispersed phase occurs is crucial in determining emulsion stability. The drainage of a thin film of the outer liquid that forms between the two drops is often the rate limiting step in this process. In this thesis, numerical simulations are used to decode the role played by fluid inertia in causing drop rebound, and the subsequent increase in drainage times, when two drops immersed in a second liquid are brought together due to a compressional flow imposed on the outer liquid. Additionally, the influence of the presence of insoluble surfactants at the drop interface is studied. It is shown that insoluble surfactants cause a dramatic increase in drainage times by two means, by causing drop rebound for small surfactant concentrations, and by partially immobilizing the interface for large surfactant concentrations.