The thesis is an exploration of the current role of the small business forest sector in hinterland forest communities, and the extent to which their economic and social positions correspond to the role envisioned for them by two prevailing visions of the future of the forest industry. One, advocated by Canadian political economists, predicts a continuation, indeed an intensification of corporate concentration, with attendant downsizing and job losses. Corporate restructuring is seen in part to induce small business development, through subcontracting arrangements and local entrepreneurialism, as a response to losses of core forest industry jobs. The second interpretation, advocated by the alternative forestry school, views the current crisis in the forest industry as an opportunity to return to decentralised approaches to ecologically-based forest management which encourage 'democracy in the forests', leading to community and environmental sustainability. Local entrepreneurs are an important part of this new 'value-based' forest economy. Interviews with small forest operators reveal a diversity of economic and social identities that do not conform well to either of the positions ascribed to small business by the Canadian political economy or alternative forestry literatures. The representations of small business found in these two literatures homogenize and suppress this diversity, making it difficult to 'see' small forest operators as anything other than contractors to the conventional system of corporate forestry, or alternative operators in an ecosystem- and community-based forest economy. In the place of these singular, marginalizing representations, I argue, using poststructural and feminist approaches to economic geography, for a 'third way' of exploring small forest operator subjectivities through overdetermined multiple class processes. Exploring small forest operator identity through multiple class processes avoids the essentialism found in fixed representations. It recognizes the transformative potential of small business in the forest economy, without denying the potential for exploitation that exists both within small business and corporate forestry. Class processes rendered invisible in the Canadian political economy and alternative forestry narratives, such as unpaid labour performed by family members and volunteer work in local planning processes, as well as work performed for wages and profit, are considered in this multiple class processes approach.

The thesis is an exploration of the current role of the small business forest sector in hinterland forest communities, and the extent to which their economic and social positions correspond to the role envisioned for them by two prevailing visions of the future of the forest industry. One, advocated by Canadian political economists, predicts a continuation, indeed an intensification of corporate concentration, with attendant downsizing and job losses. Corporate restructuring is seen in part to induce small business development, through subcontracting arrangements and local entrepreneurialism, as a response to losses of core forest industry jobs. The second interpretation, advocated by the alternative forestry school, views the current crisis in the forest industry as an opportunity to return to decentralised approaches to ecologically-based forest management which encourage 'democracy in the forests', leading to community and environmental sustainability. Local entrepreneurs are an important part of this new 'value-based' forest economy. Interviews with small forest operators reveal a diversity of economic and social identities that do not conform well to either of the positions ascribed to small business by the Canadian political economy or alternative forestry literatures. The representations of small business found in these two literatures homogenize and suppress this diversity, making it difficult to 'see' small forest operators as anything other than contractors to the conventional system of corporate forestry, or alternative operators in an ecosystem- and community-based forest economy. In the place of these singular, marginalizing representations, I argue, using poststructural and feminist approaches to economic geography, for a 'third way' of exploring small forest operator subjectivities through overdetermined multiple class processes. Exploring small forest operator identity through multiple class processes avoids the essentialism found in fixed representations. It recognizes the transformative potential of small business in the forest economy, without denying the potential for exploitation that exists both within small business and corporate forestry. Class processes rendered invisible in the Canadian political economy and alternative forestry narratives, such as unpaid labour performed by family members and volunteer work in local planning processes, as well as work performed for wages and profit, are considered in this multiple class processes approach. / Arts, Faculty of / Geography, Department of / Graduate

This thesis presents the results of investigations in two areasA) Laminar helical flow of Herschel Bulkley fluids in annular space; and B) Cuttings transport in deviated wellbores. Description of area A: This is a theoretical study that consists of the modelling of non-Newtonian fluid flowing through annular space. The rheology of the fluid is represented by a three-parameter fluid model to account for a non-linear behaviour of the rheologic curve followed by the presence of a yield stress. Two distinct methodologies were used to study the effects of inner pipe rotation and inner pipe eccentricity on the velocity profiles of the annular flow. I. Laminar Helical Flow of a Herschel-Bulkley Fluid in a Concentric Annulus and its Extension to a Narrow Eccentric Annulus: The method consists of the use of the boundary conditions to enable the numerical integration of the motion equation. The subsequent extension to eccentric annuli is based on division of the annulus into sectors, where each sector is treated as an equivalent sector of a concentric annulus. Profiles of velocity presented in 2-D and 3-D contour plots explain the effects of eccentricity, inner pipe rotation and yield stress in many different situations. This analysis is useful to simulate the flow field in a borehole during directional drilling and primary cementing particularly for narrow eccentric annuli. II. Laminar Helical Flow of a Herschel-Bulkley Fluid in an Eccentric Annulus and The Special Case of a Pure Axial Flow: A new methodology to obtain the governing equations is proposed here as a first step to the solution of this complicated problem. It consists of eliminating the unknown radial and tangential pressure gradients from the equation of motion by defining vorticity between these two components of the velocity vector. The vorticity equation and the remaining axial component of the motion equation, written in bipolar co-ordinates, are then made discrete using two different finite difference approaches. Firstly, the inertial terms of both equations are made discrete using a modified upwind scheme proposed by O. Axelsson and I. Gustafsson, while the viscous terms are made discrete using central difference approximation. Secondly, the moving boundary conditions are set by enforcing continuity of pressure on the inner annular wall. The future solution of these equations will provide a very accurate model, unavailable until now, that accounts for both effects, the eccentricity and rotation of the drill string, to simulate the flow field of drilling mud in directional and horizontal wells. Description of area B: The fluid models developed are incorporated in the development of two semi-empirical correlations to predict the critical conditions of cuttings transport in deviated weI/bore. The numerical fluid models are modified to predict the velocity of the fluid at the vicinity of the cutting that is at the point of being transported. An extensive bank of data of the critical conditions of transport, emulating many different field conditions, was used in this analysis. The experimental data was provided by an industry sponsored project which did four years of experimental work in a simulated testing column to generate the data. The two semi-empirical correlations developed in this research are based on: • a dimensional analysis of the variables involved in two distinct mechanisms of transport experimentally observed: 1. Rolling or Sliding and 2. Suspension; • a force balance applied to a cutting resting on the low-side wall of an inclined annulus, under fluid dynamic conditions. The semi-empirical correlations can be used as general criteria for evaluating and correlating the effects of various parameters on cuttings transport, and as a guideline for cuttings transport programme design during directional drilling.

L'écoulement à travers un milieu poreux d'un fluide non newtonien, est un problème récurrent rencontré dans de nombreux domaines de l'industrie et dont la difficulté réside à la fois dans la géométrie complexe du milieu poreux et dans le caractère non-linéaire des matériaux utilisés. Dans cette thèse, nous adoptons une approche différente de celle menée dans les travaux antérieurs, en nous basant principalement sur l'expérimentation. En procédant à des essais systématiques d'injection dans un milieu poreux dont nous pouvons contrôler les données géométriques, nous montrons qu'un gradient de pression seuil, étant proportionnel au seuil du fluide et inversement proportionnel à la taille typique des pores, doit systématiquement être dépassé pour mettre le fluide en écoulement.En outre, nous étudions la possibilité de regrouper, via un redimensionnement, l'ensemble des résultats sur une courbe maîtresse et établir ainsi une base pour l'établissement d'une loi générale d'écoulement / The flow of a non-newtonian fluid through a porous medium is a matter of importance in several industrial applications whose difficulty arises from both the complex geometry of the porous medium and the non-linear behaviour of the complex fluids. In this thesis we investigate the flow of Herschel-Bulkley fluids via a mainly experimental approach and aim to set a generalized law for this particular type of complex fluid in porous medium.Our experimental set-up allows us to perform systematic trials of injection in model porous media whose we can control geometrical parameters. We show that a threshold pressure gradient, proportional to the yield stress and inversely proportional to the particles mean diameter has to be systematically surpassed to make the fluid flow through the porous medium. We also investigate the possibility, thanks to a resizing, to gather all the experimental data on a master curve representative of a generalized law

L'écoulement à travers un milieu poreux d'un fluide non newtonien, est un problème récurrent rencontré dans de nombreux domaines de l'industrie et dont la difficulté réside à la fois dans la géométrie complexe du milieu poreux et dans le caractère non-linéaire des matériaux utilisés. Dans cette thèse, nous adoptons une approche différente de celle menée dans les travaux antérieurs, en nous basant principalement sur l'expérimentation. En procédant à des essais systématiques d'injection dans un milieu poreux dont nous pouvons contrôler les données géométriques, nous montrons qu'un gradient de pression seuil, étant proportionnel au seuil du fluide et inversement proportionnel à la taille typique des pores, doit systématiquement être dépassé pour mettre le fluide en écoulement.En outre, nous étudions la possibilité de regrouper, via un redimensionnement, l'ensemble des résultats sur une courbe maîtresse et établir ainsi une base pour l'établissement d'une loi générale d'écoulement

This diploma thesis deals with rheological properties of mayonnaise. The theoretical part of the thesis deals with the characterization of mayonnaise and the emulsion that mayonnaise represents, it deals with production of mayonnaise, components and storage too. Another issue is about rheological properties of foods and effects that affect them. The practical part deals with evaluation of analytical indicators, such as pH, titration acidity, fat content and dry matter and rheological properties. The aim of this thesis is to determine what type of fluid mayonnaise represents. The viscosity of samples was measured by a rotary viscometer at increasing shear rate and subsequently at constant shear rate for 300 seconds. Flow curves were created from these data, they represent dependence of shear stress on shear rate, which indicate that mayonnaise is a non-Newtonian fluid that have plastic and pseudoplastic behavior. Dependence of viscosity on time were created, it indicates that mayonnaise have thixotropic behavior. Control and adjustment of rheological properties such as viscosity provide a quality product.

Made available in DSpace on 2014-06-11T19:23:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-12-07Bitstream added on 2014-06-13T19:50:38Z : No. of bitstreams: 1 vieira_as_me_ilha.pdf: 1217264 bytes, checksum: cb21063aba699b564242c2fc4b3c3ed4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os escoamentos na superfície livre que se processam sobre forte declividade podem desenvolver instabilidades ao cabo de tempo finito. Tais instabilidades aparecem sob formas de ondas tipo “hydraulic jumps” bem espaçados e são denominadas Roll Waves. Estas ondas, longas e periódicas, podem ser contínuas ou descontínuas; contínuas em problema Shallow Water viscoso e descontínuas para o caso não viscoso. Tal fenômeno pode ser observado tanto em escoamentos naturais como em canais artificiais e vertedouros de barragens. Tratando-se de escoamento de Fluidos não newtonianos, tal fenômeno pode ser visto facilmente em lavas torrenciais, avalanchas ou “debris flows”. Nesta dissertação foram analisados matematicamente e numericamente o comportamento e as condições de existência para a formação de Roll Waves em escoamentos laminares e turbulentos. Em escoamentos turbulentos toma-se como referência os trabalhos realizados por Maciel (2001) numa reologia Binghamiana. Para escoamentos laminares, cita-se o trabalho de Mei (1994) em uma reologia tipo Power Law. No plano numérico, para escoamentos turbulentos, foram utilizadas rotinas do MATLAB® versão 6.5 e, para escoamentos laminares, rotinas em FORTRAN 90; onde pôde-se analisar e comparar resultados para diversas reologias. O foco desta dissertação foi tratar o problema Roll Waves como uma instabilidade na vizinhança do regime uniforme para Fluidos não newtonianos, em regimes turbulentos e laminares. A reologia tratada e representativa de diversos escoamentos na natureza foi a de Herschel Bulkley. A partir desta dissertação deixa-se, como perspectiva futura, um estudo mais aprofundado sob formação de ondas em fluidos hiperconcentrados tipo Herschel Bulkley com abordagem experimental a fim de validar resultados apontados nesta pesquisa. / Flows that happen over strong slope with free surface can develop instabilities after some finite time. Such wave shaped instabilities appear in the flow and are of the type “hydraulic jumps” well spaced and they are called Roll Waves. Those waves are long and periodic, continuous or discontinuous, continuous in viscous Shallow Water problems, and discontinuous for the inviscid case. Roll Waves are uncommon in natural flows, but they are common in man made channels and dams spillway. For flows of non Newtonian fluids such phenomenon can be seen easily in lava torrent, avalanche and debris flow. In this work it were mathematically and numerically analyzed the behavior and the existence conditions for the generation of Roll Waves within laminar and turbulent flows. For turbulent flows it is taken as reference the works done by Maciel (2001) dealing with a Bingham rheology. For laminar flows the reference is the work done by Mei (1994) using a Power Law rheology. Numerically, for turbulent flows it were used MATLAB® 6.5 procedures and for laminar flows FORTRAN 90 procedures were developed. Using these reference procedures it was obtained compared and analyzed results for several rheologies. This work left as future perspective a deeper study about the generation of waves in hipper concentrated fluids such as Herschel Bulkley fluid, with an experimental approach aiming to validate results produced. The focus of this work was to treat the so called Roll Waves problem as an instability in the vicinity of the uniform flow regime for non Newtonian fluids under laminar and turbulent flow regimes. The Herschel Bulkley rheology that was treated in this work is representative of several flows that happen in nature.

L'enjeu des travaux contenus dans cette thèse est la caractérisation rhéologique de suspensions concentrées d'objets viscoplastiques suspendus dans une matrice viscoplastique. Trois contraintes physiques se présentent : l'hétérogénéité des objets, la taille des objets au regard de la taille du système étudié, et la proximité entre la consistance de la phase suspendante et celle des objets. Dans notre contexte alimentaire, il faut ajouter des contraintes d'ordre biologique : les faibles durées de vie des produits, les prélèvements in vivo et la conservation des conditions de températures et d'humidité. L'ensemble de ces contraintes aboutit à une rhéométrie spécifique, aux frontières de la mécanique des milieux continues, avec pour objectif de mesurer des propriétés rhéologiques pertinentes. Pour cela, deux instrumentations originales ont été construites pour effectuer la caractérisation rhéologique le plus vite et au plus près de la génération des échantillons.Appliquée aux bols alimentaires issus de fromage, leur rhéologie vient gouverner les écoulements en bouche et induire la création de surface d'échange en bouche, au travers de la mastication. Au travers de ces interfaces, les arômes et les sapides sont libérés et transportés vers les récepteurs sensoriels. Les résultats montrent le lien entre le seuil de contrainte à l'écoulement du bol et la libération d'arômes de différents hydrophobicités, fonction de la fermeté et du taux de matières grasses du fromage. Plus particulièrement, la phase suspendante fluide, semble jouer un rôle majeur dans la création et la persistance des surfaces d'échanges. Appliquée aux jus gastriques issus de pain, l'enjeu est de savoir si des modifications des contenus en glucides pouvaient impacter la rhéologie des jus gastriques, modifier les cinétiques de vidange en sortie d'estomac, et diminuer l'excursion glycémique. Les résultats montrent l'effet d'un ajout d'amylose sur l'augmentation de la viscosité aux temps de digestion longs, lorsque la rhéologie n'est plus gouvernée par l'encombrement des particules de pain gonflées d'eau. Cependant, l'amylose ne semble pas avoir d'impact sur les cinétiques de vidange, ce qui vient conforter que le débit en sortie d'estomac est régulé par la charge énergétique contenue dans le repas. / The challenge of this work is to carry out the rheological characterization of concentrated suspensions of viscoplastic objects suspended in a viscoelastic matrix. Three structural constraints are faced: the heterogeneity of the particles, the size of particle in relation to the size of the whole system studied, and the proximity between the consistency of the suspending phase and that the consistency of the particles. In the food context, some biological constraints are added: small lifetimes of bolus, in vivo sampling and test conditions of temperature and humidity. All these constraints lead to a compromise in rheometry, at the edge of continuum mechanics, aiming to measure useful rheological properties. To carry out the rheological characterizations quickly and efficiently, two original devices has been designed trough this work. Applied to food bolus from cheese, rheology comes to govern flows in the mouth and induce the creation of exchange area in the mouth, during the chewing process. Through these interfaces, the savors and flavors are released and transported to the sensory receptors. The results show the relationship between the yield stress of the bolus and flavors release of different hydrophobic aromas, depending on the firmness and fat content of the cheeses. Specifically, fluid suspending matrix appears to play a major role in the creation and persistence of exchange area.Applied to gastric juice from bread, the issue is whether changes in carbohydrate content could impact the rheology of gastric juice, modify the kinetics of stomach flow rate, and decrease the glycemic excursion. The results show the effect of amylose addition on increasing the viscosity for long digestion time, when the rheology is no longer governed by the jamming effect of the particles made of water-swollen bread. However, amylose does not seem to have any impact on the kinetics of emptying, which reinforces that the stomach flow rate is regulated by the caloric charge contained in the meal.

É notório que a degradação ambiental vem ao longo do tempo posicionando-se como um dos principais problemas do mundo moderno. Dentre as várias questões do interesse ambiental podemos destacar a ascensão da bolha de metano, em reservatórios hidrelétricos, desde o sedimento anóxico no fundo do reservatório até a interface água atmosfera. Neste contexto, a presente tese vêm propor uma nova modelagem matemática para a ascensão da bolha axissimétrica em fluidos newtonianos/nãonewtonianos e mostrar resultados numéricos simulados. Desta forma, o estado da arte estaria elevado a posição de permitir, via Matemática e Simulação Numérica-Computacional, a análise do transporte de metano em reservatórios de hidrelétricas através da bolha / It is well-known that environmental degradation has come along the time positioning as one of the main problems from modern world. Among several questions of the environmental interest may emphasize the methane bubble rise in hydroelectric reservoirs from the anoxic sediment in the bottom of reservoir until water interface atmosphere. In this context, the current thesis has come to propose a new mathematic modeling to the rise of the axisymmetric bubble in the newtonian/non-newtonian fluids and display numerical results simulated. Therefore, the state of art would be ascended to a position to permit, via Mathematics and Computing-Numeric Simulation, the analysis of transport of methane in hydroelectric reservoirs through of bubble

Des panaches sont connus pour migrer à travers le manteau ductile et quasi-Newtonien ; alors que les dikes se fracturent et se propagent dans la lithosphère solide. Cependant, la lithosphère est en fait visco-élastique. Afin de déterminer ce qui se passe dans ce cas complexe, nous avons réalisé une étude expérimentale et numérique sur le développement de panaches thermiques dans des solutions aqueuses de Carbopol, un gel de polymères formant un réseau continu d'éponges microscopiques. Ce fluide est rhéofluidifiant et présente un seuil de contrainte σ₀, de sorte que l'écoulement ne se produit que si la contrainte locale dépasse cette valeur critique σ₀. En dessous de cette valeur, le fluide agit comme un solide élastique. Les propriétés rhéologiques des solutions peuvent être systématiquement ajustées en variant la concentration de Carbopol. Le dispositif consiste en une source locale de chaleur de puissance constante placée au centre d'une cuve cubique. Selon la valeur du rapport entre la contrainte d'origine thermique et la contrainte seuil, Y₀, on peut observer trois régimes différents. A faible Y₀<Yc₁, aucun mouvement n'est détecté ; tandis que pour Yc₁<Y₀<Yc₂ une cellule se développe, puis évolue vers un panache pour Y₀>Yc₂. Nous montrons que les paramètres critiques (Yc₁,Yc₂) dépendent fortement de la géométrie du chauffage. Des mesures simultanées de température et de champs de vitesse montrent que la morphologie du panache ressemble à un doigt, contrairement à la forme de champignon rencontrée dans les fluides newtoniens. Utilisant des simulations numériques avec une description purement visqueuse, où la rhéologie du fluide est décrite par un modèle de Herschel-Bulkley régularisé, sont suffisantes pour rendre compte de la dynamique du panache. Une étude détaillée des paramètres indiquent que la dynamique du panache est gouvernée par la compétition entre la contrainte seuil, la contrainte induite par la flottabilité et les contraintes visqueuses. Nous avons identifié deux paramètres adimensionnés : le paramètre seuil Ψ comparant la contrainte induite par la flottabilité et la contrainte seuil, et le nombre de Bingham Bi comparant la contrainte seuil et les contraintes visqueuses. Un panache ne peut s'élever que si les deux paramètres sont supercritiques, i.e. la contrainte induite par la flottabilité et les contraintes visqueuses sont plus importantes que la contrainte seuil. Par conséquent, le panache peut s'arrêter avant d'atteindre la surface. Des lois d'échelles dans le conduit du panache ont été déterminées pour la vitesse, la température et la taille de la région cisaillée en régime permanent. Elles décrivent raisonnablement le comportement du conduit bien que seul l'effet rhéofluidifiant soit pris en compte. L'application de ces paramètres adimensionnés à la Terre contraignent significativement la limite de plasticité du manteau et de la lithosphère. La contrainte seuil maximale qui permet à une instabilité thermique de pénétrer dans la lithosphère ou le manteau supérieur est entre 100 kPa et 100 MPa, et elle dépend fortement de la taille et de l'anomalie de densité de l'intrusion. / Plumes are known to migrate through the ductile quasi-Newtonian mantle, while dikes fracture and propagate through the solid lithosphere. However, depending on the timescale, the lithosphere presents solid as well as viscous properties. To determine what happens in the complex case, where instabilities propagate through a visco-elastic matrix, we performed a combined study of laboratory experiments and numerical simulations. Here we investigate the development of thermal plumes in aqueous solutions of Carbopol, a polymer gel, forming a continuous network of micrometric sponges. This fluid is shear thinning and has a yield-stress σ₀, whereby flow occurs only if the local stress exceeds this critical value σ₀. Below this value, the fluid acts as an elastic solid. The rheological properties of the solutions can be systematically varied by varying the Carbopol concentration. The setup consists of a localized heat-source operated at constant power, placed at the centre of a square tank. Depending on the ratio of the thermally induced stresses and the yield stress, Y₀, three different regimes may be obtained. For low Y₀<Yc₁ no motion occurs, whereas for Yc₁<Y₀<Yc₂ a cell develops, that evolves into a plume for Y₀>Yc₂. We show that the critical parameters (Yc₁,Yc₂) strongly depend on the geometry of the heating. Combined temperature and velocity field measurements show that the morphology of the plume resembles a finger, contrary to the mushroom-like shape encountered in Newtonian fluids. Numerical simulations using a purely viscous description, where the rheology of the fluid is described by a regularized Herschel-Bulkley model, are sufficient to capture the plume dynamics. A detailed parametric study shows that the plume dynamics are governed by the interplay between yield stress, buoyancy induced stress and viscous stresses. We identify two non-dimensional parameters: the yield parameter Ψ comparing the buoyancy induced stress to the yield stress, and the Bingham number Bi comparing the yield stress to the viscous stresses. We show that a plume can rise only if both parameters are supercritical, i.e. if buoyancy induced stress and viscous stresses each overcome the yield stress. Therefore the plume may come to a halt before it reaches the surface. We propose scaling laws for the plume stem velocity, temperature and the size of the shear zone in the steady state. We show that the scaling laws describe the behaviour in the plume stem reasonably well, if the yield stress is neglected and only the shear thinning behaviour is taken into account. Applying the non-dimensional parameters to Earth places severe constraints on the strength of mantle and lithosphere. The maximum strength that allows for thermal instabilities to penetrate the lithosphere or upper mantle is in between 100 kPa and 100 MPa, and strongly depends on the size and buoyancy of the anomaly.