Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

A common challenge during deposition of slurries is segregation as large particles settle through the matrix of fines and water. Whether segregation occurs or not depends on the grain size distribution of the solids, the void ratio or solids content and the rheological properties of the fines-water matrix. The rheological characterization of slurry composed of different grain sizes and varying water chemistry was investigated. The vane yield stress was used to characterize different slurries composed of clay, silt and sand materials. Semi-empirical fractal theory showed good agreement with experimental data for fine slurry. Comparison of yield stress at same concentration but different composition showed a decreasing trend as the composition of either silt or sand material increases. The pore-water effect was studied for representative kaolinite slurry. The yield stress was insensitive for pH values in the acidic and neutral range, while in the basic range it showed significant response depending upon the type of the chemical used to achieve the pH: Ca(OH)2 and NaOH. A modified segmented standpipe was designed and used in a series of experiments to determine concentration profiles during the sedimentation processes. Analyses of the solid content profiles and sand content profiles in the standpipes indicated a capture of sand particles which could be correlated to the yield stress of the fines matrix. Theoretical calculations, however, showed over-prediction of the captured sand size. A correction factor of about 0.2 was applied. Flume test on a high solid content slurries showed that the dynamic segregation is governed by all the factors governing the static case. Beaching profile shapes were not a necessary indication of segregating and non-segregating type of slurries. Modified version plastic theory for flow slides was used to characterise profile shape. Computational fluid dynamics approaches based on kinetic theory and bi-viscous model analysis were implemented and showed a reasonable capability in modelling segregation when compared with experimental results. A statistical formulation for segregation index, SI, was proposed. The index accounts for variation in depth of samples. Finally recommendations for future research are proposed based on the observations and findings made from the study. / Geotechnical Engineering

The rheological and structural properties of polymeric liquids cannot be condensed within a single numerical model. They should be described within hierarchical, multi-level numerical models in which each sub-model is responsible for different time and length scales; atomistic, mesoscopic, and continuum. In this study, the rheological and structural properties of linear, short-chain polyethylene liquids were investigated from the classical atomistic level to the mesoscopic and continuum levels of description. At the atomistic level of description, nonequilibrium molecular dynamics (NEMD) simulations of linear, short-chain polyethylene liquids spanning from C16H24 to C128H256 were performed to advance our knowledge of fundamental characteristic of chain molecules under shear and planar elongational flow. Furthermore, entanglement characteristics, such as the shortest primitive path length, and the network configurations, were investigated as functions of strain rate in both vastly different flow fields using the topological Z-code. At the mesoscopic level of description, Brownian dynamics (BD) simulations of a freely-jointed chain with equivalent contour length to C78H158 were carried out to compare single-chain dynamics in dense liquids (NEMD) and dilute solutions (BD) under shear flow. In addition, the macromolecular configurational diversity of individual chains in dense liquids and dilute solutions was explored using a brightness distribution method inspired by the rheo-optical investigation of DNA solutions. Based on these observations, a simple coarse-grained mesoscopic model for unentangled polymeric liquids and semi-dilute solutions was proposed and compared with NEMD simulation data and experiments of semi-dilute DNA solutions under shear flow in terms of the rheological and structural properties, such as viscosity, normal stress coefficients, conformation tensor, and so on. Moreover, this model was further coarse-grained to the continuum level through pre-averaging and compared with NEMD simulation data to examine the relationships between different levels of description on the rheological and structural properties of unentangled polymeric materials under shear flow.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Romain Valéry Roy, Dept. of Mechanical Engineering. Includes bibliographical references.

Concentrated kaolin clay slurries are found in a number of industrial operations including mine tailings surface disposal, underground paste backfill, and riverbed dredging. An understanding of the impact of solids concentration and addition of chemical species on slurry rheology is of importance to designers of pipeline transport and waste disposal systems. A project to determine the rheology of an idealized industrial kaolin clay slurry using a concentric cylinder viscometer and an experimental pipeline loop was undertaken. Additional laboratory test work including particle size analysis, slurry pH, calcium ion concentration in the slurry supernatant and particle electrophoretic mobility measurements were completed to aid in the understanding of their effects on the slurry rheology. The slurries were prepared in varying kaolin clay solids concentrations with reverse osmosis water. A flocculant, dihydrated calcium chloride (CaCl2 ¡¤ 2H2O), was added to the reverse osmosis water in concentrations equivalent to those found in typical industrial hard water supply. A dispersant, tetra-sodium pyrophosphate (TSPP, Na4P2O7) was used to disperse the clay particles for selected slurries. It was found that the kaolin clay slurries, in the absence of TSPP, exhibited yield stresses and could be characterized with either the two-parameter Bingham or Casson continuum flow models. Increasing the clay concentration in the slurry, while keeping the mass ratio of flocculant to kaolin constant, increased both the yield and plastic viscosity parameters. There was generally good agreement between the rheological parameters obtained in the Couette flow viscometer and that in the pipeline loop. In slurries for which it was possible to obtain turbulent flow, the transition to turbulent flow was predicted accurately by the Wilson & Thomas method for both Bingham and Casson models. It was possible to eliminate the yield stress of a slurry with the addition of the dispersing agent TSPP. The calcium ion content of the supernatant extracted from the slurries proved to be a indicator of the degree of flocculation. When exposed to extended periods of high shear conditions in the pipeline loop, slurries with clay concentrations of 17% by volume solids or greater exhibited an irreversible increase in apparent viscosity with time. An attempt was made to investigate this irreversible thickening characteristic. Laboratory tests did not reveal any appreciable differences in particle size, electrophoretic mobility, calcium ion concentration or pH with this irreversible change. The shear duration test shows the importance of using the appropriate shear environment when testing high solids concentration kaolin clay slurries

Concentrated kaolin clay slurries are found in a number of industrial operations including mine tailings surface disposal, underground paste backfill, and riverbed dredging. An understanding of the impact of solids concentration and addition of chemical species on slurry rheology is of importance to designers of pipeline transport and waste disposal systems. A project to determine the rheology of an idealized industrial kaolin clay slurry using a concentric cylinder viscometer and an experimental pipeline loop was undertaken. Additional laboratory test work including particle size analysis, slurry pH, calcium ion concentration in the slurry supernatant and particle electrophoretic mobility measurements were completed to aid in the understanding of their effects on the slurry rheology. The slurries were prepared in varying kaolin clay solids concentrations with reverse osmosis water. A flocculant, dihydrated calcium chloride (CaCl2 ¡¤ 2H2O), was added to the reverse osmosis water in concentrations equivalent to those found in typical industrial hard water supply. A dispersant, tetra-sodium pyrophosphate (TSPP, Na4P2O7) was used to disperse the clay particles for selected slurries. It was found that the kaolin clay slurries, in the absence of TSPP, exhibited yield stresses and could be characterized with either the two-parameter Bingham or Casson continuum flow models. Increasing the clay concentration in the slurry, while keeping the mass ratio of flocculant to kaolin constant, increased both the yield and plastic viscosity parameters. There was generally good agreement between the rheological parameters obtained in the Couette flow viscometer and that in the pipeline loop. In slurries for which it was possible to obtain turbulent flow, the transition to turbulent flow was predicted accurately by the Wilson & Thomas method for both Bingham and Casson models. It was possible to eliminate the yield stress of a slurry with the addition of the dispersing agent TSPP. The calcium ion content of the supernatant extracted from the slurries proved to be a indicator of the degree of flocculation. When exposed to extended periods of high shear conditions in the pipeline loop, slurries with clay concentrations of 17% by volume solids or greater exhibited an irreversible increase in apparent viscosity with time. An attempt was made to investigate this irreversible thickening characteristic. Laboratory tests did not reveal any appreciable differences in particle size, electrophoretic mobility, calcium ion concentration or pH with this irreversible change. The shear duration test shows the importance of using the appropriate shear environment when testing high solids concentration kaolin clay slurries

Many soft food materials, including vegetable shortening, exhibit complex rheological behaviour with properties that resemble those of a solid and a liquid simultaneously. The fundamental parameters used to describe the rheological response of vegetable shortening were obtained from uniaxial compression tests, including monotonic and cyclic compression, as well as creep and stress relaxation tests. The fundamental parameters obtained from the various compression tests were then used in two mechanical models (viscoelastic and elasto-visco-plastic) to predict the compression and conical indentation response of vegetable shortening. The accuracy of the two models was studied with the help of the commercially available finite element analysis software package Abaqus. It was determined that the viscoelastic model was not suitable for the prediction of the rheological response of shortening. On the other hand, the proposed elasto-visco-plastic model predicted with reasonable accuracy the uniaxial compression and indentation experimental response of vegetable shortening. / February 2009

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Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains ix, 110 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 54-59).