Browsing by Subject "Viscosity"
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Item Accuracy of speech-language pathologists replicating barium sulfate viscosity(Texas Tech University, 2000-04) Kopec, Katy BethChanges in bolus viscosity effect changes in oropharyngeal swallowing physiology, in some cases resulting in a more efficient swallow for dysphagic patients. Thus, systematic variation of bolus viscosity is often implemented as a diagnostic tool during the modified barium swallow evaluation. However, there is no universal standard for the definition and variation of bolus viscosity during the procedure. Clinicians rely upon subjective judgements (e.g., stirring, pouring, or "eyeing" solutions) to determine appropriate protocols. The goal for this study was to examine the relationship between subjective and objective measurements of viscosity. Two research questions were raised: Can experienced clinicians (1) accurately and (2) reliably replicate barium sulfate viscosity using only subjective judgements? Ten speech-language pathologists, experienced in performing modified barium swallow studies, attempted to replicate three barium sulfate solutions of predetermined viscosity using liquid barium sulfate (HD85'™) and water. Clinicians performed the task three times for each solution. Flow curves were obtained using a dynamic, rotational viscometer (the Rheomat RM 180™0. Viscosity (Pa s) of each sample was determined as a function of a wide range of shear rates (s"). Multiple conelation statistics indicated clinicians were neither accurate nor reliable in their attempts to match solution viscosity using only subjective judgements. These results suggest a need for reevaluation of ciurent diagnostic procedures employed in dysphagia management. The potential usefulness of rheologically defined barium sulfate protocol and the need for additional research in this area are discussed.Item Axisymmetric flow of dilute xanthan gum polymer solutions through media(Texas Tech University, 1984-08) Duran, Stephen LynnNot availableItem Coupling of linear and angular momentum in concentrated suspensions of spheres(Texas Tech University, 2003-08) Feng, ShihaiIn Newtonian fluids, the proportionality constant that relates the flux of linear momentum to gradients in the velocity is the shear viscosity. Similarly, the flux of angular momentum is related to gradients in the spin field by the spin viscosity for simple fluids. In fluids in which external torque per unit volume is applied, the equations of linear and angular momentum are coupled. In simple fluids, the equations are coupled through the vortex viscosity, which relates the transfer of angular to linear momentum to the difference in the local spin rate and one-half of the vorticity of the fluid. Apparent viscosity is normally measured, for example, in a pressure driven flow experiment, as a proportionality constant that relates the force acted on system and the volume flow rate of the system. The purpose of this study is to evaluate shear viscosity, vortex viscosity, and spin viscosity in suspensions by solving the coupled momentum equations and study their relationships to the apparent viscosity and energy dissipation. In this study, we investigated the influence of particle spin imposed by external torque on the apparent viscosity of non-colloidal suspension by using a simulation based on the boundary element method (BEM). The numerical results reveal that particles spin has a pronounced effect on apparent viscosity of the suspension. For example, in suspension subjected to a pressure gradient in a tube, vary the spin gradient from positive to negative by exerting external torque on the particles, the apparent viscosity changes from close to zero to infinite with asymptotic change to apparent negative viscosity. Apparent "negative" viscosity is due to torque driven flow through vortex viscosity that is the proportionality constant between the transfer of the linear to angular momentum flux and the difference between the spin rate and the one-half local vorticity. Measurements of vortex viscosities from the numerical experiments agreed the theoretical prediction of vortex viscosity of dilute suspensions and extended the results to concentrated suspensions. The energy efficiency of torque driven flow is compared to the energy efficiency of force driven flow. External torques are applied to neutrally buoyant particles in boundary element simulations to generate a cubic velocity profile in a suspension confined in a rectangular channel. The quantitative values of spin viscosity are determined as a function of solids fraction by calculating the volume averaged stress and kinematics of these flows and combining these results with a theoretical analysis of the coupled equations describing the conservation of linear and angular momentum. Many configurations of particles at each concentration are generated and analyzed until reproducible averages of the spin viscosity at each solids fraction are determined. The scaling of the spin viscosity with the square of the particle size predicted in earlier theoretical studies is verified in this investigation. The conservation equation describing the rate of energy dissipation in suspensions is derived, and the contributions due to spin viscosity are included. The energy dissipation rate is shown to consist of the linear combination of terms that include the shear viscosity, vortex viscosity and spin viscosity. Predictions from these equations using the coefficients determined in the this work are compared with the energy dissipation rates obtained from a macroscopic balance using the force and velocity on the boundaries of the suspension in numerical simulations of a number of different flow fields. Over the range of our data, these independent predictions are shown to be in excellent agreement for both dilute and concentrated suspensions.Item Discontinuous Galerkin Finite Element Method for the Nonlinear Hyperbolic Problems with Entropy-Based Artificial Viscosity Stabilization(2012-07-16) Zingan, Valentin NikolaevichThis work develops a discontinuous Galerkin finite element discretization of non- linear hyperbolic conservation equations with efficient and robust high order stabilization built on an entropy-based artificial viscosity approximation. The solutions of equations are represented by elementwise polynomials of an arbitrary degree p > 0 which are continuous within each element but discontinuous on the boundaries. The discretization of equations in time is done by means of high order explicit Runge-Kutta methods identified with respective Butcher tableaux. To stabilize a numerical solution in the vicinity of shock waves and simultaneously preserve the smooth parts from smearing, we add some reasonable amount of artificial viscosity in accordance with the physical principle of entropy production in the interior of shock waves. The viscosity coefficient is proportional to the local size of the residual of an entropy equation and is bounded from above by the first-order artificial viscosity defined by a local wave speed. Since the residual of an entropy equation is supposed to be vanishingly small in smooth regions (of the order of the Local Truncation Error) and arbitrarily large in shocks, the entropy viscosity is almost zero everywhere except the shocks, where it reaches the first-order upper bound. One- and two-dimensional benchmark test cases are presented for nonlinear hyperbolic scalar conservation laws and the system of compressible Euler equations. These tests demonstrate the satisfactory stability properties of the method and optimal convergence rates as well. All numerical solutions to the test problems agree well with the reference solutions found in the literature. We conclude that the new method developed in the present work is a valuable alternative to currently existing techniques of viscous stabilization.Item Experimental Assessment of Water Based Drilling Fluids in High Pressure and High Temperature Conditions(2012-10-19) Ravi, AshwinProper selection of drilling fluids plays a major role in determining the efficient completion of any drilling operation. With the increasing number of ultra-deep offshore wells being drilled and ever stringent environmental and safety regulations coming into effect, it becomes necessary to examine and understand the behavior of water based drilling fluids - which are cheaper and less polluting than their oil based counterpart - under extreme temperature and pressure conditions. In most of the existing literature, the testing procedure is simple - increase the temperature of the fluid in steps and record rheological properties at each step. A major drawback of this testing procedure is that it does not represent the continuous temperature change that occurs in a drilling fluid as it is circulated through the well bore. To have a better understanding of fluid behavior under such temperature variation, a continuous test procedure was devised in which the temperature of the drilling fluid was continuously increased to a pre-determined maximum value while monitoring one rheological parameter. The results of such tests may then be used to plan fluid treatment schedules. The experiments were conducted on a Chandler 7600 XHPHT viscometer and they seem to indicate specific temperature ranges above which the properties of the drilling fluid deteriorate. Different fluid compositions and drilling fluids in use in the field were tested and the results are discussed in detail.Item Highly concentrated, nanoclusters of self-crowded monoclonal antibodies for low viscosity, subcutaneous injections(2011-05) Miller, Maria Andrea; Maynard, Jennifer Anne, 1974-; Johnston, Keith P., 1955-; Edgar, Thomas; Truskett, Thomas; Williams, III, Robert O.Delivery of protein therapeutics is restricted to intravenous infusions due to protein-dependent problems including low solubilities, high viscosities, and physical instabilities. The ability to inject high concentrations of proteins via subcutaneous injections would increase accessibility and compliance. Large particles of a protein in a non-aqueous solvent can decrease the viscosity over a solution of equally concentrated individual protein molecules. The lower viscosity of a particle suspension is due to decreased surface area resulting in reduced electroviscous effects, solvation and deviations of the particle shape from a spherical geometry. Additional studies show that aqueous-based dispersions of antibody nanoclusters can be formed by increasing the attractive interactions between protein molecules using the excluded volume effects of extrinsic crowding agents. These novel, equilibrium, nanoclusters are maintained by a balance of highly attractive interactions and weak electrostatic repulsive interactions near the protein’s pI. These protein nanoclusters are ideal for subcutaneous delivery as they have low interactions between the colloids, are reversible in nature, and dissolve rapidly upon dilution in a buffer media. Through in vivo mouse studies, the bioavailability of a monoclonal antibody in the dispersion is prolonged and higher doses can be administered versus a solution. Overall, these studies with high concentration, low viscosity subcutaneous injections of protein therapeutics open new opportunities in biotechnology. For oral delivery of itraconzole, controlled flocculation of individual polymerically-stabilized nanoparticles is used to increase supersaturation. Flocculation of these nanoparticles is achieved by desolvating the polymer by changing the pH. The flocculated dispersions can then be easily filtered. The final amorphous powder maintains high supersaturation with simulated stomach and small intestine conditions and improves bioavailability of itraconazole, over the commercial product, Sporanox®.Item Identification and characterization of non-flammable azeotropic mixtures for precision cleaning(2017-04-18) Perry, Jacob; Williams, Darren L.; Gross, Dustin E.; Thompson, David E.The goal of this thesis is to provide methods that can be used to search for new azeotropes with specific desired properties, and methods to characterize these new azeotropes. All azeotrope possibilities that were examined in this study were low-boiling azeotropes composed of non-aqueous solvents, and the desired properties were for the azeotropes to be non-flammable and have good solvency against hydrocarbon grease. In this study, azeotropes were formed for use in cleaning applications, specifically vapor degreasing. For cleaning applications, the most important quality of the azeotrope is solvency. However, in a vapor degreaser flammability is an issue. To obtain the desired solvency in an azeotrope, the Hansen Solubility Parameters (HSPs) were used to decide what solvents were good candidates. However, the solvents that were found from this search were flammable. In an attempt to get the desired properties, the solvents were paired with non-flammable solvents that had similar boiling points to obtain a blend with good solvency and no flammability. Then, these pairs were mixed and distilled to identify whether the pairs formed low-boiling azeotropes. The resulting azeotropes were characterized by obtaining their boiling point, flash point, thermal expansion coefficient, surface tension, density, viscosity and composition. The boiling points were obtained from the distillation process. The flash points were found using a modified ASTM D56 method. Thermal expansion coefficients were obtained through the dependence of the density on temperature. The surface tension and density were obtained using a DuNouy ring tensiometer. Viscosity was found using a ball drop viscometer. Finally, the composition was found using Raman spectroscopy. All these standard procedures can be found in the appendix. A solubility parameter-based model for predicting azeotropic behavior in binary mixtures was explored as an extension of the results of this thesis work. The goal of this model is to predict the likelihood that a given pair of solvents will form a low-boiling azeotrope. Such a model would save time in the laboratory, reduce personnel exposure, and reduce waste by steering the researchers away from unpromising mixtures that are unlikely to form azeotropes.Item The manufacture and characterization of protein nanoclusters(2013-05) Dinin, Aileen Kathryn; Johnston, Keith P., 1955-; Maynard, Jennifer Anne, 1974-The ability to formulate monoclonal antibodies at high concentration in a low-viscosity form is of broad interest in drug delivery, as monoclonal antibody-based drugs are now prescribed for cancer, autoimmune disorders, and many other diseases. Herein, we create highly concentrated antibody dispersions (up to 260 mg/mL) via three different methods, utilizing proline as an interacting depletant or trehalose as a non-interacting depletant. These dispersions are able to achieve viscosities an order of magnitude lower than similarly concentrated antibody solutions over a range of formulation pHs. When diluted, these antibody dispersions return to monomer. The proline acts to minimize protein zeta potential, thus reducing the electrostatic repulsion on the protein, even when formulated 3 pH units away from the antibody pI. In addition, it acts as a depletant, forcing the monomers into cluster via osmotic effectsItem Mass transfer area of structured packing(2010-05) Tsai, Robert Edison; Eldridge, R Bruce; Rochelle, Gary T.; Bonnecaze, Roger T.; McGlamery, Gerald G.; Seibert, A Frank; Truskett, Thomas M.The mass transfer area of nine structured packings was measured as a function of liquid load, surface tension, liquid viscosity, and gas rate in a 0.427 m (16.8 in) ID column via absorption of CO₂ from air into 0.1 mol/L NaOH. Surface tension was decreased from 72 to 30 mN/m via the addition of a surfactant (TERGITOL[trademark] NP-7). Viscosity was varied from 1 to 15 mPa·s using poly(ethylene oxide) (POLYOX[trademark] WSR N750). A wetted-wall column was used to verify the kinetics of these systems. Literature model predictions matched the wetted-wall column data within 10%. These models were applied in the interpretation of the packing results. The packing mass transfer area was most strongly dictated by geometric area (125 to 500 m²/m³) and liquid load (2.5 to 75 m³/m²·h or 1 to 30 gpm/ft²). A reduction in surface tension enhanced the effective area. The difference was more pronounced for the finer (higher surface area) packings (15 to 20%) than for the coarser ones (10%). Gas velocity (0.6 to 2.3 m/s), liquid viscosity, and channel configuration (45° vs. 60° or smoothed element interfaces) had no appreciable impact on the area. Surface texture (embossing) increased the area by 10% at most. The ratio of effective area to specific area (a[subscript e]/a[subscript p]) was correlated within limits of ±13% for the experimental database: [mathematical formula]. This area model is believed to offer better predictive accuracy than the alternatives in the literature, particularly under aqueous conditions. Supplementary hydraulic measurements were obtained. The channel configuration significantly impacted the pressure drop. For a 45°-to-60° inclination change, pressure drop decreased by more than a factor of two and capacity expanded by 20%. Upwards of a two-fold increase in hold-up was observed from 1 to 15 mPa·s. Liquid load strongly affected both pressure drop and hold-up, increasing them by several-fold over the operational range. An economic analysis of an absorber in a CO₂ capture process was performed. Mellapak[trademark] 250X yielded the most favorable economics of the investigated packings. The minimum cost for a 7 m MEA system was around $5-7/tonne CO₂ removed for capacities in the 100 to 800 MW range.Item Performance prediction of cavitating propulsors using a viscous/inviscid method(2008-08) Sun, Hong, active 2008; Kinnas, Spyros A.A viscous/inviscid interaction method for predicting the effect of viscosity on the performance of wetted and cavitating propulsors is presented. The emphasis is placed on steady wetted and cavitating propulsor flows. A three-dimensional low order potential based boundary element method is strongly coupled with a two dimensional integral boundary layer analysis method based on the strip theory assumption. The influence of viscosity on the outer inviscid flow is modeled through the wall transpiration model by distributing “blowing” sources on the propulsor blade and trailing wake surfaces. The boundary layer edge velocities are expressed as the sum of the inviscid edge velocity and a correction which depends only on the boundary layer variables. The influence of outer potential flow on the inner boundary layer flow is considered through the edge velocities. In the case of sheet cavitation, a “thin” cavity approach is employed and the viscous/inviscid interaction method is applied on the blade surface underneath the cavity. On the cavity surface, the friction force coefficient is forced to be zero. Numerical predictions by the present viscous/inviscid interaction method are presented for open, ducted, and water-jet propulsors. For water-jet propulsors, the flow is solved in an iterative manner by solving the rotor and stator problems separately and by considering the time-averaged effects of one component on the other. Predicted forces, pressure distributions, and boundary layer variables are compared with those predicted by other numerical methods and experimental measurements.Item Item A study of microemulsion viscosity with consideration of polymer and co-solvent additives(2014-05) Dashti, Ghazal; Delshad, MojdehWith the dramatic increase in the worldwide demand for the crude oil and with the fact that the oil and gas resources are depleting, the enhanced oil recovery process plays an important role to increase the production from the existing hydrocarbon reservoirs. Chemical enhanced oil recovery is one of the most important techniques to unlock significant amount of trapped oil from oil reservoirs. Surface agent materials (Surfactants) are used to lower the interfacial tension (IFT) between water and oil phases to ultralow values and mobilize the trapped oil. When surfactant, water, and oil are mixed together they form a thermodynamically stable phase called microemulsion which can be characterized by ultralow interfacial tension and the ability to solubilize both aqueous and oil compounds. Another characteristic of microemulsion solution is its viscosity which plays an important role in the creation and movement of the oil bank. The microemulsion micro-structure is complex and its viscosity is difficult to predict. Various viscosity models and correlations are presented in the literature to describe microemulsion viscosity behavior, but they fail to represent the rheological behavior of many microemulsion mixtures. Most of these models are valid in the lower and higher ranges of solute where one of the domains is discontinuous. The majority of the models fail to calculate the rheology of microemulsion phase in bicontinuous domains. In this work, we present a systematic study of the rheological behavior of microemulsion systems and the effect of additives such as polymer and co-solvent on rheological properties of microemulsions. Several laboratory experiments were conducted to determine the rheological behavior of surfactant solutions. A new empirical model for the viscosity of microemulsion phase as a function of salinity is introduced. The model consists of three different correlations one for each phase type of Windsor phase behaviors. The proposed model is validated using a number of experimental results presented in this document. The proposed viscosity model is implemented in the UTCHEM simulator and the simulator results are compared with the coreflood experiments. Excellent matches were obtained for the pressure. We further improved the proposed viscosity model to incorporate the effect of polymer and co-solvent on the microemulsion viscosity.Item Transport properties of polystyrene above and below the glass transition temperature(Texas Tech University, 1983-12) Fike, Lawrence RobertIn the production of expandable polystyrene (EPS) foam, it is desirable to be able to predict the density of the final product by some means other than empirical estimates. Therefore, a mathematical model was developed to predict the density of EPS during a prepuffing expansion process. Use of the mathematical model requires some knowledge of the fundamental properties of viscosity, shear modulus, and mass diffusion coefficients for water and n-pentane through polystyrene. Since expansion is induced by thermal stimulus, these properties must be known as a function of temperature. The theoretical and experimental development in measuring these parameters constitute the bulk of the text in this thesis. A very simplistic Maxwell model for viscoelastic behavior was used as the basis for the theoretical development in the determination of the viscosity and shear modulus of polystyrene. Mass diffusion coefficients for water and n-pentane in polystyrene were determined by a solution to Fick's second law with appropriate initial and boundary conditions. Once the parameters had been determined, they were fit to an Arrhenius type model in order to determine temperature dependence. The transport properties were observed to be strongly affected by the polymer's glass transition. Finally, a computer program was developed and used to predict the density of EPS as a function of time during the expansion process.Item Using Nanotechnology in Viscoelastic Surfactant Stimulation Fluids(2012-11-12) Gurluk, Merve Rabia 1986-Viscoelastic surfactant (VES) fluids are preferred for many applications in the oil industry. Their viscoelastic behavior is due to the overlap and entanglement of very long wormlike micelles. The growth of these wormlike micelles depends on the charge of the head group, salt concentration, temperature, and the presence of other interacting components. The problem with these fluids is that they are expensive and used at temperatures less than 200?F. The viscoelasticity of nanoparticle-networked VES fluid systems were analyzed in an HP/HT viscometer. A series of rheology experiments have been performed by using 2-4 vol% amidoamine oxide surfactant in 13 to 14.2 ppg CaBr2 brines and 10.8 to 11.6 ppg CaCl2 brines at different temperatures up to 275?F and a shear rate of 10 s-1. The nanoparticles evaluated were MgO and ZnO at 6 pptg concentration. In addition, the effect of different nanoparticle concentrations (0.5 to 8 pptg) and micron size particles on the viscosity of VES fluid was investigated. The oscillatory shear rate sweep (100 to 1 s-1) was performed from 100 to 250?F. The effect of fish oil as an internal breaker on the viscosity of VES micelles was examined. This study showed that the addition of nanoparticles improved the thermal stability of VES micellar structures in CaBr2 and CaCl2 brines up to 275?F and showed an improved viscosity yield at different shear rates. Micro- and nanoparticles have potential to improve the viscosity of VES fluids. Lab tests show that for VES micellar systems without nanoparticles, the dominant factor is the storage modulus but when nanoparticles are added to the system at 275?F the loss modulus becomes the dominant factor. These positive effects of nanoparticles on VES fluid characteristics suggest that these particles can reduce treatment cost and will exceed temperature range to 275?F. With this work, we hope to have better understanding of nanoparticle/viscoelastic surfactant interaction.Item Viscosities of natural gases at high pressures and high temperatures(Texas A&M University, 2007-09-17) Viswanathan, AnupEstimation of viscosities of naturally occurring petroleum gases provides the information needed to accurately work out reservoir-engineering problems. Existing models for viscosity prediction are limited by data, especially at high pressures and high temperatures. Studies show that the predicted viscosities of natural gases using the current correlation equations are about 15 % higher than the corresponding measured viscosities at high pressures and high temperatures. This project proposes to develop a viscosity prediction model for natural gases at high pressures and high temperatures. The project shows that commercial gas viscosity measurement devices currently available suffer from a variety of problems and do not give reliable or repeatable results. However, at the extremely high pressures encountered in high pressure and high temperature reservoirs, the natural gases consist mainly of methane as the hydrocarbon constituent and some non-hydrocarbon impurities. Available viscosity values of methane were used in the development of a correlation for predicting the viscosities of naturally occurring petroleum gases at high pressures and high temperatures. In the absence of measurements, this correlation can be used with some confidence.