Dissertationen zum Thema „Fluid-Grain“

Systemic hydration, plasma electrolytes, ingesta and fecal hydration and gastrointestinal passage of cobalt (after CoEDTA administration via nasogastric tube) in horses fed large grain meals or treated with enteral fluid therapy, IV fluid therapy and enteral laxatives were investigated. In the first study, 0.9% NaCl (10 L/h/8h) was administered slowly via a small-bore nasogastric tube or as 10 L boluses via a large-bore nasogastric tube to four normal horses. In the other studies, horses with a right dorsal colon fistula were used. To create the right dorsal colon fistula, a cannula with 5 cm internal diameter was implanted 2 to 6 weeks after a right dorsal colopexy had been created. Six horses with the right dorsal colostomy were alternately used to test three feeding regimes for 48 h: 1- hay free choice; 2- hay free choice plus 4.5 kg of sweet feed twice daily after a period of 5 days of adaptation; 3- sudden change from hay to hay plus sweet feed. Seven horses with the right dorsal colostomy were alternately used to test 6 experimental conditions while fasted for 24 h: 1- control (no treatment), 2- enteral MgSO4 (1 g/kg), 3- enteral Na2SO4 (1 g/kg), 4- IV lactated Ringer's solution (5 L/h/12 h), 5- enteral water (5 L/h/12 h), 6- enteral electrolyte solution (5 L/h/12 h). In the last study, four horses with the right dorsal colostomy were alternately treated with enteral electrolyte solution (10 L/h/6h) and enteral MgSO4 (1 g/kg) plus IV fluid therapy (10 L/h/6h). Despite the administration regimen, enteral administration of 0.9% NaCl produced diarrhea, hypernatremia and hyperchloremia. Colostomy allowed serial collection of large ingesta samples. Grain ingestion did not change PCV or plasma protein, but affected plasma electrolytes and produced dehydration of ingesta and formation of frothy ingesta. Fasting delayed gastrointestinal transit. Enteral fluid therapy was the most effective treatment in promoting ingesta hydration. Enteral water, MgSO4, Na2SO4, IV fluid therapy and enteral MgSO4 plus IV fluid therapy were either ineffective in promoting ingesta hydration or produced marked plasma electrolyte imbalance. These findings support the use of enteral fluid therapy in horses with gastrointestinal impaction.
Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.
Includes bibliographical references (p. 67-79).
We present a discrete element model for simulating, at the grain scale, gas migration in brine-saturated deformable media. We rigorously account for the presence of two fluids in the pore space by incorporating forces on grains due to pore fluid pressures, and surface tension between fluids. This model, which couples multiphase fluid flow with sediment mechanics, permits investigating the upward migration of gas through a brine-filled sediment column. We elucidate the ways in which gas migration may take place: (1) by capillary invasion in a rigid-like medium; and (2) by initiation and propagation of a fracture. We find that grain size is the main factor controlling the mode of gas transport in the sediment, and show that coarse-grain sediments favor capillary invasion, whereas fracturing dominates in fine-grain media. The results have important implications for understanding vent sites and pockmarks in the ocean floor, deep sub-seabed storage of carbon dioxide, and gas hydrate accumulations in ocean sediments and permafrost regions. Our results predict that, in fine sediments, hydrate will likely form in veins following a fracture-network pattern. In coarse sediments, the buoyant methane gas is likely to invade the pore space more uniformly, in a process akin to invasion percolation, and the overall pore occupancy is likely to be much higher than for a fracture-dominated regime. These implications are consistent with laboratory experiments and field observations of methane hydrates in natural systems.
by Antone Kumar Jain.
S.M.

Analyses of fluid inclusions and microstructures within the Papoose Flat pluton were used to investigate the chemistry and temperatures of fluids circulating with the pluton during cooling. Based on previous microstructural analyses, the interior of this late Cretaceous granitic to granodioritic pluton has been divided into three domains: i) a central core characterized by magmatic microstructures, ii) a middle domain of high temperature (>500°C) solid-state deformation, and iii) an outermost domain characterized by relatively low temperature (<5000°C) solid-state deformation. According to previously published anisotropy of magnetic susceptibility analyses and pluton cooling models, plastic flow occurred in both the outer part of the pluton and within its aureole rocks while the core of the pluton was still molten. Solid-state deformation is proposed to have stopped when the pluton interior cooled through its solidus less than 100,000 years after magma emplacement.

Microstructural analysis of samples from all three domains confirmed the transition from magmatic flow in the core of the pluton to solid-state deformation at the pluton margin. However, weakly developed solid-state microstructures overprint the dominant magmatic microstructures in samples from the core domain. The existence of solid-state microstructures in all three domains indicates that deformation continued during and after crystallization of the interior of the pluton.

Two phase, low salinity (< 26 wt% NaCl equivalent), liquid-rich aqueous fluid inclusions predominate within both quartz and feldspar grains in all samples. Throughout the pluton, the majority of fluid inclusions are hosted by deformed grains. Feldspar-hosted primary inclusions are associated with sericitic alteration. Inclusions were also observed in feldspar as secondary or pseudosecondary inclusions along fractures. Inclusions in quartz are frequently found near lobate grain boundaries or near triple junctions; linear pseudosecondary inclusion assemblages are commonly truncated against lobate boundaries between adjacent quartz grains, indicating that discrete microcracking events occurred during plastic deformation.

Homogenization temperatures overlap for all three microstructural domains. Coexisting andalusite and cordierite in the contact aureole, and the intersection of the Mus + Qtz dehydration reaction with the granite solidus, indicate trapping pressures between 3.8 and 4.2 kb. Ninety-eight percent of the calculated fluid inclusion trapping temperatures at 3.8 - 4.2 kb are below the granite solidus of 650°C. Seventy-six percent of the trapping temperature data fall within the more restricted range of 350-500°C; i.e. at temperatures which are lower than the commonly cited brittle-ductile transition temperatures for feldspar at natural strain rates, but above those for quartz. No correlation could be established between trapping temperatures and either host mineral or microstructural domain within the pluton.

The similar, relatively low trapping temperatures indicate that the majority of inclusions preserved in all three domains were trapped during the late low strain magnitude stages of solid-state deformation. The most common fluid inclusion trapping temperatures (400-500°C) in all three microstructural domains are similar to the deformation temperatures indicated by microstructures and crystal fabrics in the outer part of the pluton; these trapping temperatures are obviously lower than temperatures associated with contemporaneous solid state and magmatic flow in the pluton interior. The similar trapping temperatures within the pluton core and margin must indicate that the inclusion-trapping event migrated from the margin to the core of the pluton as it cooled, because fluid inclusions would rapidly equilibrate to a density appropriate for the PT conditions of their host minerals.
Master of Science

Computational fluid dynamics, analytical solutions, and mathematical modelling approaches are used to gain insights into the distribution of fumigant gas within farm-scale, grain storage silos. Both fan-forced and tablet fumigation are considered in this work, which develops new models for use by researchers, primary producers and silo manufacturers to assist in the eradication grain storage pests.

Nowadays, consumers are increasingly aware of diet related health problems and therefore demand natural and safe ingredients as an alternative to synthetic substances, which are commonly used in the food, pharmaceutical and cosmetic industry. This idea is supported by the consumer’s concern about the safety of products containing synthetic chemicals because these synthetic molecules are suspected to cause or promote negative health effects. Recent studies showed that phenolic and carotenoid compounds are important bioactive compounds with human health benefits. However, the development of new functional foods requires technologies for incorporating these ingredients into food in order to use and protect sensitive food components, to ensure protection against nutritional loss, to mask or preserve flavors/aromas and transform liquids into easy to handle solid ingredients. In many cases, microencapsulation can provide the necessary protection for these compounds and among various techniques that can be employed to form microcapsules, spray drying appears to be a well-established and widely used technique. In this contest, propolis, one of the few natural remedies that has maintained its popularity over a long period of time, represents a widely available natural substance very rich in bioactive compounds that have plenty of biological and pharmacological properties, such as immunomodulatory, antitumor, antiinflammatory, antioxidant, antibacterial, antiviral, antifungal, antiparasite activities, among others. Moreover, it is well known that by-products of plant origin represent also an abundant source of sugars, minerals, organic acid, dietary fibre and phenolics which have a wide range of action which includes antitumoral, antiviral, antibacterial, cardio protective and antimutagenic activities for which, however, strategies for their extraction must be developed. With increasing concerns over the use of organic solvents and their disposal, supercritical fluid extraction (SFE), with carbon dioxide (CO2) as solvent and ethanol (EtOH) as co-solvent, is becoming a promising alternative. In particular, due to low cost and high content of value-added products, such as ferulic and pcoumaric acids, brewer’s spent grain, the major by-product of brewing industry, produced in large quantities annually and generally used as feeding stuff, can be used as an attractive adjunct in human nutrition. Moreover, by-products of orange fruits processing industries represent also a promising sources of materials which may be used in the food industry because of their valuable technological and nutritional properties. Hence, the aim of the study was to enhance the antioxidant properties of fish burgers with microencapsulated propolis and extracts from brewer’s spent grain and orange by-products. In particular, spray-drying process was used to microencapsulate propolis (30 g in 100 mL of ethanol 70% v/v) by means of gum Arabic and Capsul in different ratios (1:6 for gum Arabic and Capsul and then 1:20 just for Capsul). Once defined the optimal microencapsulation conditions, an alcohol-free powder able to mask the strong odor of propolis was obtained, thus promoting a potential food application as source of phenolics and antioxidants. Specifically, 5% w/w of spraydried propolis was incorporated in fish burgers. To improve their sensory properties, new ingredients such as potato flakes (3%, 5%, 7% and 10% w/w) and extra virgin olive oil (9% w/w) were tested and optimized to give a final fish product with good acceptability. Proper tests on burgers also demonstrated an effective increase of both phenolic content and antioxidant activity. Then, to extract bioactive compounds from brewer’s spent grain (BSG9 a proper supercritical fluid extraction (SFE) was found. The effects of three factors including pressure (15–35 MPa), temperature (40–60°C) and ethanol concentration (0–60%, v/v) were investigated. Among the extraction variables, the best conditions (35 MPa of pressure, 40°C of temperature and 60% ethanol) were found considering the criterion of maximum concentration of phenolic compounds (0.35 ± 0.01 mg/g BSG), flavonoids (0.22 ± 0.01 mg/g BSG) and antioxidant potential, evaluated by the ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical (2.09 ± 0.04%/g BSG). After, the optimal BSG extract was microencapsulated and finally added to the fish-burger formulation. In particular, microencapsulation was performed by means of a spray-drying, using Capsul as wall material, and modifying inlet temperatures (90-120-150°C) and ratios between extract and carrier (1:2; 1:4; 1:6; 1:8). Lastly, a sensory evaluation on the fish-burgers prepared with the different bioactive powders was carried out in order to establish the best combination of operating parameters. The sample with 5% microencapsulated BSG extract and Capsul solution in ratio equal to 1:2 at 150°C was chosen as the best compromise according to chemical characterization of active powder and sensory evaluation of sample. To finish, the antioxidant properties of fish burger with microencapsulated BSG extract were compared to the control. Results confirmed the potential use of BSG as food ingredient to increase the nutritional quality of fish burgers. Finally, the potential use of orange by-products, traditionally used as molasses for animal feed, fibre (pectin) and for fuel production, as a source of functional compounds and their application in fish burger has been demonstrated. Two SFE and spray drying techniques were comparing; in particular have been used methods found in the literature and techniques identified previously for the BSG, that appeared the best thanks to a final product of good quality with a higher polyphenols, flavonoids and carotenoids content. Then, different percentages of this powder were added to the fish burger until its overall sensory quality reached sensory threshold. 5% of powder represented the highest concentration to be used; in fact fish-burger loaded with this percentage showed both overall quality statistically similar to that of the control sample and an increase of bioactive compound content

Les écoulements granulaires sont des systèmes complexes et évolutifs dans lesquels les grains interagissent entre eux et, s'ils sont immergés, avec un fluide. Ces écoulements se produisent à différentes vitesses et contraintes, et peuvent se comporter comme des solides, des liquides ou même des gaz. Les écoulements granulaires sont impliqués dans de nombreux phénomènes et à de nombreuses échelles, depuis les écoulements de masse géophysiques tels que les glissements de terrain, les écoulements pyroclastiques et les avalanches de neige, jusqu'aux processus industriels tels que les produits pharmaceutiques, la production alimentaire et la construction. Par souci de simplicité, les écoulements granulaires sont généralement étudiés avec une distribution monodisperse de grains. Cependant, parmi ces écoulements, les grains impliqués dans ces processus ont des tailles différentes, une propriété appelée polydispersité.Cette thèse se concentre sur l'étude des écoulements granulaires et sur l'influence de la polydispersité sur les écoulements granulaires. Nous explorons l'effet de la polydispersité sur les écoulements à faible inertie et à forte inertie. En outre, nous étudions les écoulements granulaires secs et immergés dans la configuration d'effondrement de la colonne granulaire.Nous étudions les écoulements granulaires avec de méthodes expérimentales et numériques. Les simulations numériques des écoulements granulaires sont réalisées à l'aide de méthodes d'éléments discrets (DEM) et, pour les cas immergés, nous utilisons une méthode d'éléments finis couplée à des DEM. Nous menons également une campagne expérimentale dans l'appareil d'essai triaxial où nous faisons varier le niveau de polydispersité, dans le but d'étudier la résistance des matériaux granulaires polydispersés dans des conditions quasi-statiques. En outre, nous procédons à la modélisation physique des écoulements gravitaires immergés et secs dans la colonne granulaire. Notre objectif est d'explorer l'influence de la polydispersité sur les écoulements et d'identifier l'influence de la pression du fluide sur la mobilité. Pour les expériences, nous utilisons des grains sphériques, en nous concentrant exclusivement sur l'effet de la polydispersité sur les écoulements granulaires.Nos résultats nous permettent de conclure que la résistance au cisaillement des matériaux granulaires est indépendante de la polydispersité, depuis une condition quasistatique jusqu'à une condition de forte inertie. Pour des conditions d'inertie très importantes, la résistance au cisaillement des matériaux polydispersés est plus faible que celle des matériaux monodispersés. Nous avons constaté que cette différence provient de variations distinctes des paramètres géométriques et de force appartenant au réseau de contact et de force. En outre, nous démontrons que les écoulements granulaires immergés sont fortement influencés par une augmentation des niveaux de polydispersité. Nous montrons que la différence entre les matériaux monodispersés et polydispersés provient essentiellement de différentes évolutions de la pression de base du fluide. L'initiation des écoulements polydisperses est retardée par rapport aux écoulements monodisperses, en raison d'une variation négative soutenue de la pression du fluide avec une grande amplitude. Ensuite, lorsque l'écoulement se dépose, les systèmes polydisperses atteignent des distances plus longues en raison de la génération d'une pression interstitielle excédentaire qui dure plus longtemps que la pression interstitielle excédentaire provoquée par les systèmes monodisperses. Enfin, nous proposons un modèle qui relie l'énergie cinétique à la mobilité des écoulements granulaires, qui s'applique à différents niveaux de polydispersité et qui a été validé avec succès par des simulations et des expériences. Les résultats de cette thèse apportent de nouvelles connaissances sur le rôle de la polydispersité dans les écoulements granulaires secs et immergés
Granular flows are complex and evolving systems where grains interact with each other and, if immersed, interact with an ambient fluid. These flows occur at different velocities and state variables, and could behave like solids, liquids or even gases. Granular flows are involved in many circumstances and scales, from geophysical mass flows such as landslides, debris flows, pyroclastic flows, and snow avalanches, to industrial processes like pharmaceuticals, food production, and construction. For simplicity, granular flows are commonly studied with a monodisperse distribution of grains (e.i., grains with nearly the same size); however, among these flows, the grains involved in these processes have different sizes, a property termed as polydispersity.This thesis focuses on the study of granular flows and, specifically, on the influence that polydispersity has on granular flows. We explore the effect that polydispersity has on steady flows with low inertia, where granular materials can be considered as solids, and high inertia, where granular materials can be considered as fluids. Additionally, we study dry and immersed granular flows in the granular column collapse configuration, that is a benchmark geometry for studying granular flows with phases of acceleration and deceleration.We study granular flows by means of experimental and numerical methods. The numerical simulations of granular flows are done with discrete element methods (DEM) and, for immersed cases, we use a coupled finite element method (FEM) with DEM. We also conduct a controlled experimental campaign in the triaxial test apparatus where we systematically vary the polydispersity level, aiming to study the strength of polydisperse granular materials in quasi-static conditions. Furthermore, we do the physical modelling of immersed and dry gravity-driven flows in the granular column collapse configuration. Our goal is to explore the influence of polydispersity on granular flows and to identify the influence of the basal fluid pressure on the mobility of granular flows. For the experiments, we use spherical beads, exclusively focusing on the effect that size polydispersity has on granular flows.Our results allow us to conclude that the shear strength of granular materials is independent of the size polydispersity from a quasistatic condition to a condition of high inertia. For very large inertial conditions, the shear strength of polydisperse materials is smaller compared to that of monodisperse materials. We found that this difference arises from distinct variations in geometric and force parameters belonging to the contact and force network. Additionally, we provide evidence that immersed granular flows are strongly influenced by an increase in polydispersity levels. We show that the difference between monodisperse and polydisperse materials essentially arises from different evolutions of the basal fluid pressure. The initiation of polydisperse flows is delayed compared to monodisperse flows, due to a sustained negative fluid pressure change with large amplitude. Then, as the flow deposits, polydisperse systems reach longer runout distances due to the generation of exceeding pore pressure that lasts longer than the exceeding pore pressure provoked by monodisperse systems. Finally, we propose a model that links flow kinetic energy with the mobility of granular flows, which applies to different polydispersity levels, and has been successfully validated through simulations and experiments. The results of this thesis provide new insights into the role of polydispersity in both dry and immersed granular flows

In Canada, about 60% of contaminated sites involve petroleum hydrocarbon (PHC) contamination and most of these sites have been abandoned due to contamination. Among current technologies used for soil remediation, supercritical fluid extraction (SFE) is a relatively recent and potentially viable method. The main aim of this research was to investigate the application of SFE for removal of PHCs from contaminated soils. In the first phase, the effects of SFE operational parameters including fluid pressure, fluid temperature, time duration and mode of extraction on the removal efficiency of PHCs from a spiked sandy soil (with diesel fuel with a ratio of 5 wt%) were investigated. SFE experiments were performed at different pressures (15, 33 and 50 MPa) and temperatures (30, 75 and 120 °C). The combination of 10 min static mode followed by 10 min dynamic mode, repeated for 3 cycles (60 min in total) led to the highest PHC removal percentage. According to response surface methodology (RSM), the optimum pressure and temperature were found to be 50 MPa and 69.3 °C, respectively. According to experimental results, the optimum combination of pressure and temperature determined to be 33 MPa and 75 °C; which resulted in the extraction percentages of 99.2%, 91.7% and 86.1% for PHC F2, F3 and F4 fractions, respectively. In the second phase, the influence of several parameters including soil water content, soil pH and addition of modifier on PHCs removals from a field-contaminated sandy soil using SFE were experimentally investigated. SFE experiments were performed at 33 MPa pressure and temperatures of 45 and 75 °C. Three water content levels of 8%, 14% and 20% at two levels of pH 6.5 and 7.5 were investigated. The extraction of total petroleum hydrocarbon fractions (TPHF), the sum of F2, F3, and F4 fractions, decreased due to the increase in the water content from 8% to 20% at both pH 6.5 and 7.5. The difference of extractions of all PHC fractions at pH values of 6.5 and 7.5 were not statistically significant (at p < 0.05 confidence level) at all three water content levels and pH did not have a significant influence on the PHC removal efficiency. Addition of acetone as a modifier (33.7% TPHF removal) was more effective than hexanes (24.3% TPHF removal) to decrease the concentrations of PHCs for the field contaminated soil. In the third phase, the influence of soil texture and grain size on the extraction of PHC fractions was investigated. SFE experiments were performed at 33 MPa pressure and 75 °C temperature. Three types of soils (soil A, B and C) were spiked with diesel fuel with a ratio of 5 wt%. Soil A, B and C had different particle sizes and were categorized as sand, silt loam and clay, respectively. Soil A (sand) which had the largest particle size resulted in the highest TPHF removal percentage while soil C (clay) with the smallest particle size led to the lowest TPHF removal percentage. A higher clay content in soil C resulted in a lower extraction of PHCs. In the fourth phase, the effects of pressure and temperature on the extraction of PHC fractions from a clay soil spiked with diesel fuel with a ratio of 5 wt% were investigated. SFE experiments were performed at three pressures (15, 33 and 50 MPa) and temperatures (30, 75 and 120 °C). According to the statistical analysis including factorial design and RSM, the optimized combination of pressure and temperature was selected at 42.8 MPa and 120 °C; which resulted in the removal percentages of 74.9% and 65.6% for PHC F2 and F3 fractions, respectively. The optimum combination of pressure and temperature based on the experimental results was selected at 33 MPa and 120 °C that led to 70.3%, 58.4% and 32.6% removal of PHC F2, F3 and F4 fractions, respectively.

Turbulent bedload transport represents the main contribution to the riverbed morphological evolution, and associates the non-trivial collective granular behavior with a turbulent fluid flow. Therefore, its description is both a scientific challenge and a societal issue. The present numerical approach focuses on the granular phase characterization, and considers idealized steady uniform bedload transport, with monodisperse spherical beads and a unidirectional fluid flow. This simplified configuration allows to study the underlying physical mechanisms.A minimal coupled numerical model is proposed, associating a three dimensional discrete element method with a one-dimensional volume-averaged fluid momentum balance resolution. The model is compared with classical experimental results of dimensionless sediment transport rate as a function of the Shields number. The comparison is extended to granular depth profiles of solid volume fraction, solid velocity and sediment transport rate density in quasi-2D bedload transport configurations. Parameter sensitivity analysis evidenced the importance of the fluid-particle phase coupling, and showed a robust agreement of the model with the experiments. The validated model is further used to analyze the granular depth structure in bedload transport. Varying the channel inclination angle and the specific density, it is shown that the classical Shields number and dimensionless sediment transport rate formulations do not take appropriately into account the effects of these two parameters. Analyzing the solid depth profiles and the continuous two-phase flow equations, the neglected fluid flow inside the granular bed is identified as the missing contribution. Its importance is enhanced near the transition to debris flow. A rescaling of the Shields number is proposed and is shown to make all the data collapse onto a master curve when considering the dimensionless sediment transport rate as a function of the modified Shields number. Lastly, the bedload transport granular rheology is characterized by computing locally the stress tensor as a function of the depth. The lowermost part is shown to follow a creeping regime and exhibits signature of non-local effects. The dense granular flow on the top of it, is well described by the mu(I) rheology and is observed to persist up to unexpectedly high inertial numbers. It is characterized by the co-existence of frictional and collisional contributions. The transition from dense to dilute granular flow is controlled by the Shields number, the slope and the specific density. Saltation is observed in the uppermost granular layer. These findings improve the understanding of bedload transport granular mechanisms and challenge the existing granular rheologies
Turbulent bedload transport represents the main contribution to the riverbed morphological evolution, and associates the non-trivial collective granular behavior with a turbulent fluid flow. Therefore, its description is both a scientific challenge and a societal issue. The present numerical approach focuses on the granular phase characterization, and considers idealized steady uniform bedload transport, with monodisperse spherical beads and a unidirectional fluid flow. This simplified configuration allows to study the underlying physical mechanisms.A minimal coupled numerical model is proposed, associating a three dimensional discrete element method with a one-dimensional volume-averaged fluid momentum balance resolution. The model is compared with classical experimental results of dimensionless sediment transport rate as a function of the Shields number. The comparison is extended to granular depth profiles of solid volume fraction, solid velocity and sediment transport rate density in quasi-2D bedload transport configurations. Parameter sensitivity analysis evidenced the importance of the fluid-particle phase coupling, and showed a robust agreement of the model with the experiments. The validated model is further used to analyze the granular depth structure in bedload transport. Varying the channel inclination angle and the specific density, it is shown that the classical Shields number and dimensionless sediment transport rate formulations do not take appropriately into account the effects of these two parameters. Analyzing the solid depth profiles and the continuous two-phase flow equations, the neglected fluid flow inside the granular bed is identified as the missing contribution. Its importance is enhanced near the transition to debris flow. A rescaling of the Shields number is proposed and is shown to make all the data collapse onto a master curve when considering the dimensionless sediment transport rate as a function of the modified Shields number. Lastly, the bedload transport granular rheology is characterized by computing locally the stress tensor as a function of the depth. The lowermost part is shown to follow a creeping regime and exhibits signature of non-local effects. The dense granular flow on the top of it, is well described by the mu(I) rheology and is observed to persist up to unexpectedly high inertial numbers. It is characterized by the co-existence of frictional and collisional contributions. The transition from dense to dilute granular flow is controlled by the Shields number, the slope and the specific density. Saltation is observed in the uppermost granular layer. These findings improve the understanding of bedload transport granular mechanisms and challenge the existing granular rheologies

Forced convective drying using a wind turbine mechanically connected to a ventilation fan was hypothesized for low cost and rapid grain drying in developing countries. The idea was tested using an expandable wind turbine blade system with variable pitch, at low wind speeds in a wind tunnel. The design was based on empirical and theoretical models embedded in a graphical user interface (GUI) created to estimate airflow-power requirements for drying ear corn. Output airflow (0.0016 - 0.0052 m3kg-1s-1) increased within the study wind speed range (2.0 - 5.5 m/s). System efficiency peak (8.6%) was observed at 3.5 m/s wind speed. Flow resistance was overcome up to 1m fill depth in 0.5 m x 0.5 m wide drying bin. Drying study at different airflow rates (no forced convection, 0.002 m3kg-1s-1 and 0.008 m3kg-1s-1) were conducted in a controlled environment at 35oC and 45% relative humidity with mean drying time; 40.3, 37.9 and 22.9 h respectively, that reduced with increasing airflow while drying the ear corn from 22% to 15% moisture content. The overall result supports the hypothesis that the wind convection system increased grain drying rates and should be further developed.

The objective of this work was to examine the impact of unsteady flows on the erosion and movement of mixed grain size sediment. Time varying flows were examined as flowrates in natural rivers are rarely constant. There are very few reported studies on the movement of sediment in unsteady open channel flow and most of those used single sized sediment. River reach has its own sedimentological character and non-uniform beds exhibit very different behaviour from that of single sized material. Therefore it was thought important to examine the impact of time varying flow on the stability of water worked mixed grain size sediment beds. The thesis reports on a series of laboratory experiments in which a bimodal sediment bed was exposed to different flow hydrographs. The flow hydrographs consisted of constant flowrate with different duration and time varying flows with different rising and falling limb but had the same peak flowrate. Each experiment was followed by a stability test in which a standard "triangular shaped hydrograph" was used to assess the stability of each water worked deposit. The stability observation demonstrated that grain size fractions have different thresholds of motion when beds are formed by different antecedent flow patterns. The bed stability increased as the antecedent constant flow hydrograph progressed. The rising and falling limbs of the flowrate hydrographs were found to have a significant effect on the bed stabilisation process. It revealed that the shortest rising limb of flow hydrograph formed the weakest bed while the longest recession limb of flow hydro graph formed the most stable bed. It is believed that the short period of flowrate acceleration did not allow the coarse grains to stabilise with numerous exposed large grains spread on the bed. In a longer duration of recession limb of hydrograph, the coarse grains moved and eventually deposited over a length of time. As the flowrate declined the finer grains also rolled and then deposited forming a strong bond with the coarse grams. These experiments also provided important information on the flow structures and the changes in the bed topography as the tests progressed. There is strong evidence that only upward interactions (ejections) with high momentum magnitude were able to transport coarser grains. The lack of change in the distribution of downward looking-bed interactions (sweeps) in all tests indicated that these features are not important in determining transport. Changes in bed topography were also measured and characteristics of the distribution of bed surface elevation were linked to the observed changes in bed stability.

Flows of grain-fluid mixtures are commonly observed in nature and in industry. However, comprehensive understanding of the physics behind them is to date out of reach. This thesis aims to investigate the mechanism underlying flowing grain-fluid mixtures by both analytical and numerical methods. The work of this thesis starts with introducing standard mixture theory to describe the balance equations of mass and momentum for the fluid and the granular phases of grain-fluid mixtures. As the first step, the flowing mixtures are idealized to be saturated media, indicating that the fluid phase fills all the voids between the particles. Accordingly, the granular phase is treated as a frictional Coulomb-like media, while the fluid phase is modelled as a Newtonian fluid. The interaction forces between the two phases include buoyancy force and drag force. Taking into account the flow characteristics that the flow depth is much smaller than the flow length, the thin-layer approximation and the depth-averaged technique are employed to eliminate the dependency of the governing equations on the vertical coordinate, so that a set of depth-averaged equations are derived. The depth-averaged equations are analyzed in terms of steady flows down an inclined plane. It is found that the present model equations can interpret the classical cross-stream profiles of the downslope velocity, the blunt shape of the flowing front, and roll waves. Additionally, the depth-averaged equations are numerically resolved by using a high-resolution scheme with respect to a large-scale unsteady flow, and the numerical results are compared with the experimental data. The comparison demonstrates that this model is capable to describe dynamics of a grain-fluid mixture flow, such as the evolutions of the mixture height and volume fractions. Moreover, unsaturated grain-fluid mixtures are considered, in which the fluid phase cannot fill all interstices of the granular medium. To investigate their dynamic process, it is assumed that the fluid percolates easily down through the interstices of the granular medium and as a result the air is extruded. To describe such a kind of unsaturated mixtures, a two-layer approach is proposed, in which the fluid-saturated granular layer is overlaid by the pure granular material. The upper granular mass is treated as a frictional Coulomb-like medium, and the lower layer is described by the standard mixture theory. The lower and upper layers interact at an interface which is a material surface for the fluid phase, but across which the mass exchange for the granular phase may take place. The proposed model equations are numerically resolved, and the numerical solutions demonstrate that the proposed two-layer model can provide reasonable predictions with respect to dynamic process of unsaturated mixture flows. The last part of this thesis focuses on the improvement of the saturated depth-averaged model, presented in the first part of the thesis, by taking the granular dilatancy into account. The granular dilatancy is described by the critical-state theory. By coupling critical-state theory and mixture theory, we uncover the coupling between the granular dilatancy and the pore fluid pressure, i.e., the granular dilatancy yields the deviation of the pore fluid pressure from the hydrostatic value that, in turn, affects the motion of the granular phase. The formulated model equations describe the coupling of flow thickness, depth-averaged volume fractions and depth-averaged velocities, and the pore fluid pressure. Moreover, a numerical simulation is performed, and quantitative comparison with experimental data is reported. The comparison demonstrates that the proposed depth-averaged equations can provide reasonable predictions on the evolutions of dynamic quantities for a grain-fluid mixture flow. It is noted that this thesis is based on the accepted publications (see Meng & Wang (2015a) and Meng & Wang (2015b) and manuscripts in Meng et al. (2016) and Meng & Wang (2016).

This study was conducted to determine water intake. Forty-four Holstein bull calves were evaluated to investigate the effects of starter intake, body weight, temperature and time to predict water intake. A model was developed using PROC GLM in SAS. Least square means separation were used to identify significant effects. Starter intake was a significant variable (P < 0.05) in predicting the water intake of a calf, especially after day 21 when starter intake and water intake were both increasing. Water intake was increased by calves with fecal scores of 1 and 2. However, water intake was significantly different for calves with fecal scores of 3 or 4 with a (P < 0.05) which had decreased water intake. The interaction between scours and fecal score were not significant. Water intakes significantly differ in calves that had scour and in calves not experimented scours.

Macroscopic transport properties of porous media depend on textural rock parameters such as porosity, grain size and grain shape distributions, surface-to-volume ratios, and spatial distributions of cement. Although porosity is routinely measured in the laboratory, direct measurements of other textural rock properties can be tedious, time-consuming, or impossible to obtain without special methods such as X-ray microtomography and scanning electron microscopy. However, by using digital three-dimensional pore-scale rock models and physics-based algorithms researchers can calculate both geometrical and transport properties of porous media. Therefore, pore-scale modeling techniques provide a unique opportunity to explore explicit relationships between pore-scale geometry and fluid and electric flow properties. The primary objective of this dissertation is to investigate at the pore-scale level the effects of grain shapes and spatial cement distribution on macroscopic rock properties for improved understanding of various petrophysical correlations. Deposition and compaction of grains having arbitrary angular shapes and various sizes is modeled using novel sedimentation and cementation pore-scale algorithms. Additionally, the algorithms implement numerical quartz precipitation to describe preferential cement growth in pore-throats, pore-bodies, or uniform layers. Subsequently, petrophysical properties such as geometrical pore-size distribution, primary drainage capillary pressure, absolute permeability, streamline-based throat size distribution, and apparent electrical formation factor are calculated for several digital rock models to evaluate petrophysical correlations. Furthermore, two geometrical approximation methods are introduced to model irreducible (connate) water saturation at the pore scale. Consolidated grain packs having comparable porosities and grain size distributions but various grain shapes indicate that realistic angular grain shape distribution gives the best agreement of petrophysical properties with experimental measurements. Cement volume and its spatial distribution significantly affect pore-space geometry and connectivity, and subsequently, macroscopic petrophysical properties of the porous media. For example, low-porosity rocks having similar grain structure but different cement spatial distribution could differ in absolute permeability by two orders of magnitude and in capillary trapped water saturation by a factor of three. For clastic rocks with porosity much higher than percolation threshold porosity, pore-scale modeling results confirm that surface-to-volume ratio and porosity provide sufficient rock-structure character to describe absolute permeability correlations. In comparison to surface-to-volume ratio, capillary trapped (irreducible) water saturation exhibits better correlation with absolute permeability due to weak pore space connectivity in low-porosity samples near the percolation threshold. Furthermore, in grain packs with fine laminations and permeability anisotropy, pore-scale analysis reveals anisotropy in directional drainage capillary- pressure curves and corresponding amounts of capillary-trapped wetting fluid. Finally, results presented in this dissertation indicate that pore-scale modeling methods can competently capture the effects of porous media geometry on macroscopic rock properties. Pore-scale two- and three-phase transport calculations with fast computers can predict petrophysical properties and provide sensitivity analysis of petrophysical properties for accurate reservoir characterization and subsequent field development planning.
text

The movement of low viscosity fluid through a porous medium containing extremely viscous fluid is emerging as an important phenomenon in several petroleum engineering applications. These include the recovery of heavy oil by solvent injection, the preferential reduction of water flow using polymer gels, and the enhancement of acid fracturing treatments. The displacement of one fluid from a porous medium by a second, immiscible fluid has been extensively studied in two cases: when capillary forces are dominant, and when viscous forces are comparable to capillary forces. This dissertation research examines a third case: when viscous forces are dominant. The viscosity of the fluid initially present in the porous medium is four or more orders of magnitude greater than the viscosity of the displacing fluid. Consequently, the displacement through an individual pore will be dictated by the hydrodynamic forces required to move the high viscosity fluid. However, very little is known about grain-scale behavior of such displacements. The research will develop a mathematical model of the viscosity-dominated displacement in a network of conduits. By neglecting pressure drop within the low viscosity fluid, the model will treat the displacement as a moving boundary problem. The high viscosity fluid will be assumed Newtonian and will move in response to the pressure gradient imposed via the low viscosity fluid. The movement can be treated as pseudo-steady state flow of the highviscosity fluid. The flow field will be updated whenever the low viscosity fluid advances into a pore previously occupied by high-viscosity fluid. Swept volume will be calculated in each run for comparison and further investigation. We will use classical methods for direct and iterative solutions of large, sparse linear systems to compute these steady states. Key practical insights to be obtained from the model are the nature of the displacement and effects of geometry and hydraulic conductivities on the sweep efficiency. The model will form the basis for examining additional physical processes, notably mass transfer between fluids, and the possibility that fingering of the low viscosity fluid occurs within individual pore throats.

A pore-scale understanding of fluid flow underpins the constitutive laws of continuum-scale porous media flow. Porous media flow laws are founded on simplified pore structure such as the classical capillary tube model or the pore-network model, both of which do not include diverging-converging pore geometry in the direction of flow. Therefore, modifications in the fluid flow field due to different pore geometries are not well understood. Thus this may translate to uncertainties on how flow in porous media is predicted in practical applications such as geological sequestration of carbon dioxide, petroleum recovery, and contaminant’s fate in aquifers. To fill this gap, we have investigated the role of a spectrum of diverging-converging pore geometries likely formed due to different grain shapes which may be due to a variety of processes such as weathering, sediment transport, and diagenesis. Our findings describe the physical mechanisms for the failure of Darcy’s Law and the characteristics of Forchheimer Law at increasing Reynolds Number flows. Through fundamental fluid physics, we determined the forces which are most responsible for the continuum-scale porous media hydraulic conductivity (K) or permeability. We show that the pore geometry and the eddies associated therein significantly modify the flow field and the boundary stresses. This has important implications on mineral precipitation-dissolution and microbial growth. We present a new non-dimensional geometric factor β, a metric for diverging-converging pore geometry, which can be used to predict K. This model for K based on β generalizes the original and now widely-used Kozeny (1927) model which was based on straight capillary tubes. Further, in order to better quantify the feasibility of geological CO2 sequestration, we have conducted laboratory fluid flow experiments at reservoir conditions to investigate the controls of media wettability and grain shapes on pore-scale capillary trapping. We present experimental evidence for the snap-off or formation of trapped CO2 ganglion. The total trapping potential is found to be 15% of porosity for a water-wet media. We show that at the pore-scale media wettability and viscous-fingering play a critical role in transport and trapping of CO2. Our investigations clearly show that that in single-phase flow pore geometry significantly modifies pore-scale stresses and impacts continuum-scale flow laws. In two-phase flows, while the media wettability plays a vital role, the mobility ratio of CO2 - brine system significantly controls the CO2 capillary trapping potential- a result which should be taken into consideration while managing CO2 sequestration projects.
text

Les travaux de recherche menés dans cette thèse de doctorat se sont focalisés sur la compréhension des interactions graphène-plasma dans le cas de l’exposition de graphène polycristallin à un plasma d’argon pouvant contenant du diborane (B2H6). Une attention particulière est portée sur la cinétique de génération de dommage dans un plasma d’argon pur. Ainsi dans le cas d’un plasma continu, l’absence de seuil en énergie pour la génération de dommage due à un bombardement ionique est mis en évidence. Ceci ne peut s’expliquer que par une gravure à deux étapes, facilitée par la densité ionique élevée caractéristique des plasmas inductifs opérés en mode H. La caractérisation Raman des échantillons exposés au plasma montre une large distribution sur la petite zone sondée. Afin de relier ces fluctuations à l’état initial du graphène, l’imagerie Raman (RIMA) est adaptée dans le but d’extraire des données quantitatives sur l’état du graphène et utilisée pour le reste des travaux. Par la suite, l’étude temporelle des plasmas pulsés en puissance permet de trouver des conditions opératoires avec une fluence ionique drastiquement diminuée. Les traitements subséquents combinés aux analyses RIMA ont permis de suivre l’évolution de l’état du graphène et de distinguer l’état des joints du graphène des domaines de croissance. Ainsi, pour la première fois, l’autoréparation des joints de grains dans un matériau 2D est mis en évidence expérimentalement. Cet effet, théorisé dans les matériaux 3D mais difficilement observé expérimentalement, était effectivement prédis dans le cas du graphène. De plus, un contrôle fin des conditions opératoires du plasma pulsé d’argon a permis d’extraire des paramètres plasmas dans lesquels les métastables d’argons puis les photons VUV émis par les états résonants de l’argon sont les principaux vecteurs d’énergie. Suivant la même méthodologie que précédemment, ces traitements ont mis en lumière les rôles respectifs des ions, des métastables et des photons VUV dans la transmission d’énergie du graphène. Enfin, l’introduction de 5% de diborane a pour conséquence une modification radicale des paramètres physique du plasma. L’exposition de graphène à ce graphène à ce plasma démontre l’intérêt de cette technique pour l’incorporation élevé de bore tout en minimisant la génération de dommages
The research realized in this PhD thesis focuses on the understanding of plasma-graphene interactions during exposure of polycrystalline graphene films to a low-pressure argon RF plasma containing diborane (B2H6). A particular attention is devoted to the kinetics driving the damage formation dynamics. In the case of a continuous, argon plasma, the absence of energy threshold for the production of ion-induced damage is demonstrated. This is explained by two-step etching, facilitated by the high number density of charged species in the H-mode of RF plasmas. Raman characterization of plasma-treated graphene films shows a wide distribution over the small area surveyed. In order to link these fluctuations to the initial state of graphene, Raman imaging (RIMA) is adapted to extract quantitative data on the state of graphene before and after plasma treatment. Subsequently, the temporal study of argon RF plasmas in the pulsed regime makes it possible to find operating conditions with a drastically reduced fluence of charged species compared to the continuous regime; in combination with RIMA studies, this allows temporally- and spatially-resolved investigations of plasma-graphene interactions. For the first time, a preferential self-healing of ion-irradiation damage at grain boundaries of graphene films is experimentally demonstrated. Moreover, by using several electrical and optical diagnostics of the argon plasma in the pulsed regime, it is possible to determine operating conditions in which either the ions, the metastables or the VUV photons emitted by the resonant states become the main energy vectors. From these experiments, the respective roles of each of these species in the physics of plasma-graphene interactions could be highlighted. Finally, the introduction of 5% of diborane into the argon plasma induces a radical modification of the physicochemical properties of the plasma. Exposure of graphene films to this highly reactive plasma reveals high boron incorporation with minimal ion and hydrogen damage.

The phenomenon of particle retention in granular materials has a wide range of implications. For agricultural operations, these particles can be contaminants transported through the ground that can eventually reach to aquifers, consequently contaminating the water. In oil reservoirs, these particles can be clays that get detached from the rock and migrate with the flow after a change of pressure, plugging the reservoir with the consequent reduction in permeability. These particles can also be traceable nanoparticles, introduced in the reservoir with the purpose of identifying bypassed oil. For all these reasons it is important to understand the mechanisms that contribute to the transport and retention of these particles. In this dissertation the retention of micro and nano size particles was investigated. In saturated model sediments (sphere packs), we analyzed the retention of particles by the mechanism of straining (size exclusion). The analysis focused on experiments reported in the literature in which particles smaller than the smallest pore throats were retained in the sediment. The analysis yields a mechanistic explanation of these observations, by indentifying the retention sites as gaps between pairs of sediment grains. A predictive model was developed that yields a relationship between the straining rate constant and particle size in agreement with the experimental observations. In unsaturated granular materials, the relative contributions of grain surfaces, interfacial areas and contact lines between phases to the retention of colloidal size particles were investigated. An important part of this analysis was the identification and calculation of the length of the contact lines between phases. This estimation of contact line lengths in porous media is the first of its kind. The algorithm developed to compute contact line length yielded values consistent with observations from beads pack and real rocks, which were obtained independently from analysis of high resolution images. Additionally, the predictions of interfacial areas in granular materials were consistent with an established thermodynamic theory of multiphase flow in porous media. Since there is a close relationship between interfacial areas and contact lines this supports the accuracy of the contact line length estimations. Predictions of contact line length and interfacial area in model sediments, combined with experimental values of retention of colloidal size particles in columns of glass beads suggested that it is plausible for interfacial area and contact line to contribute in the same proportion to the retention of particles. The mechanism of retention of surface treated nanoparticles in sedimentary rocks was also investigated, where it was found that retention is reversible and dominated by attractive van der Waals forces between the particles and the rock’s grain surfaces. The intricate combination of factors that affect retention makes the clear identification of the mechanism responsible for trapping a complex task. The work presented in this dissertation provides significant insight into the retention mechanisms in relevant scenarios.
text