Les milieux granulaires, dans leur état dense, se présentent sous la forme deux régimes, un régime « solide » qui représente un état bloqué des particules et un régime fluide. La première partie de ce travail porte sur le régime fluide du milieu granulaire. Dans un premier temps, le modèle de rhéologie non-locale y est présenté et discuté au regard des modèles proposés dans la communauté. Afin de tester le modèle sur un système réel, nous présentons une expérience d’avalanche dans un canal étroit, dans lequel l’état de contrainte est hétérogène et permet ainsi de faire coexister les deux régimes. L’ajustement du modèle pose la question de la définition des conditions aux limites. Nous présentons alors une étude numérique par simulation de dynamique moléculaire en plan incliné afin d’ajuster le modèle et mesurer la condition à la surface libre. La seconde partie de la thèse porte sur le régime bloqué du milieu granulaire et plus précisément sur la mesure des modules élastiques proche de la transition. A la limite de rigidité du matériau, les propriétés élastiques disparaissent mais le module élastique en cisaillement s’annule plus vite que le module en compression. Ainsi, nous présentons une étude de propagation d’ondes acoustiques en compression permettant de mesurer les modules élastiques à des pressions de confinement évanescentes, au moyen de vols paraboliques. Nous proposons un modèle de contact inter-particulaire permettant d’expliquer la dépendance du module élastique à la pression et ainsi d’appréhender les différentes lois d’échelles évoquées dans la littérature. Enfin, nous présentons des résultats préliminaires portant sur la propagation d’ondes de cisaillement. / In their dense state, granular media can either flow like fluids or behave like solids, when they are jammed. The first part of this thesis deals with the flowing regime. We begin by presenting the non-local rheology and discuss this model with respect to the other ones proposed in the community. In order to probe this model, we perform experimental measurements of the velocity profile in an avalanche flow in a narrow channel. This setup allows to observe both the fluid regime and the creep of the supposedly jammed region, in the depth of the channel. We probe the non-local model on the experimental results. The fit of the theory raises the question of the definition of the boundary conditions on such system. We therefore perform molecular dynamic simulations on an incline plane setup in order to fit the non-local model and measure the free surface boundary condition.The second part of this thesis investigates the elastic properties of jammed granular media weakly confined. Near the rigidity (jamming) transition of the medium, elastic moduli decrease and exhibit different scaling laws in their dependence on the confining pressure. We therefore perform acoustic measurements of compression waves at vanishing pressures, by the mean of parabolic flights. We then revisit the model of inter-particle contacts. This enables to predict the elastic behavior of the medium over a wide range of pressures: from evanescent to high pressures, at which the prediction from the mean field approach using the Hertz contact model has been shown to be valid. Last, we present preliminary results of shear wave propagations.

Les coulées de laves sont les produits volcaniques les plus représentatifs des éruptions effusives. Elles sont formées quand le magma est extrudé et se répand à la surface de la Terre. Quand la lave arrive en surface, elle perd de la chaleur et refroidit. Le refroidissement affecte directement les propriétés rhéologiques de la lave, jusqu’à arrêter son écoulement. Les paramètres rhéologiques qui contrôlent la dynamique des coulées de laves sont la viscosité et le seuil de plasticité, qui dépendent eux-mêmes de la composition chimique, de la cristallinité et de la teneur en bulles. Il existe de nombreux modèles d’estimation de la rhéologie, la plupart développés pour les coulées de lave basaltiques et quelque uns pour les coulées de lave andésitiques. Les coulées de laves peuvent grandement affecter les régions peuplées, les infrastructures et l’environnement. Un moyen de prévoir les futurs dégâts est de développer des modèles numériques pour prévoir la propagation des coulées de laves sur des topographies volcaniques réelles. Cette méthode difficile combine la topographie, la rhéologie, la perte de chaleur et la dynamique de l’écoulement pour simuler l’emplacement d’une coulée de lave précise. Le code numérique VolcFlow, qui est basé sur une approche moyennée verticale, est capable de reproduire les caractéristiques principales des dépôts comme la morphologie, la longueur et l’épaisseur. Dans cette étude sont proposés trois modèles implémentés dans VolcFlow et ayant pour but de simuler des coulées de laves. Le premier est isotherme, le deuxième inclut le refroidissement et les variations rhéologiques associées, et le troisième prend en considération la déformation de la croûte à la surface de la coulée et son effet sur l’emplacement de la coulée. Afin de vérifier la validité des différentes approches, les modèles sont testés sur quatre cas d’étude : deux coulées de lave de composition basaltique (expérience de basalte fondu de Syracuse lava Project et la coulée de lave d’août novembre 2015 du Piton de la Fournaise, France) et deux de compositions andésitique (la coulée de lave du 4-5 décembre 2015 du Tungurahua et trois coulées de lave du Reventador, Equateur). Les résultats des simulations montrent que le modèle isotherme peut reproduire les coulées même s’il ne prend pas en compte les variations de rhéologie et le refroidissement. Le modèle incluant la cristallisation, induite par le refroidissement de la lave au cours de son écoulement, et les variations rhéologiques associées donne de très bons résultats mais est très sensible aux paramètres d’entrée, en particulier à la viscosité, elle-même très dépendante de la composition chimique et de la température. Enfin, le modèle prenant en compte le refroidissement et les variations de rhéologie par une loi synthétique sigmoïde montre une bonne cohérence dans tous les cas simulés, sauf pour le Piton de la Fournaise. Le modèle visant à simuler la formation d’une croûte à la surface de la lave et sa percée par l’écoulement sous-jacent amène uniquement à l’épaississement de la croûte. Le mécanisme de percée n’est pas reproduit avec VolcFlow. / Lava flows are the most representative volcanic products of effusive eruptions and are formed whenthe magma is extruded and flows on the surface. When lava flows reach the surface they lose heat and cool.Cooling affects directly the rheology of the lava up to a point where it cannot flow anymore. Rheologicalparameters that control the dynamics of lava flows are the viscosity and the yield strength which in turndepends on the chemical composition, crystallinity and bubble content. There exist numerous models forthe rheology estimation, mostly developed for basaltic lava flows and few for andesitic ones.Lava flows can highly affect populated areas, infrastructures and environment. A way to forecastthe future damages is to developed numerical codes of the lava propagation on real volcanic topography.This challenging method combines the topography, the rheology, the heat loss, and flow dynamics tosimulate the emplacement of a particular lava flow. The numerical code VolcFlow which is based on thedepth-averaged approach is able to reproduce the main physical characteristics of the deposits likemorphology, length and thickness. Here 3 models are proposed for their implementation in VolcFlow withthe aim to simulate lava flows. One model is isothermal, the second includes cooling and the associatedrheological variations, and the third takes into account the crust formation and its effect on the flowemplacement. To check the validity of the different approaches, the models were tested with four studycases, two with basaltic compositions (molten basalt experiment of the Syracuse lava Project and the August-November, 2015 lava flow from Piton de la Fournaise, France) and two with andesitic compositions (theDecember 4th-5th lava flow from Tungurahua, Ecuador, and three lava flows from El Reventador,Ecuador). Results of the simulations shows that the isothermal model can reproduce the flows even if itdoes not consider the cooling and rheology variation. The model that includes rheological laws as functionof crystallization induced by cooling down flow can give very good results but is very sensitive to the inputdata, in particular to the fluid viscosity that is very dependent on chemical composition and temperature.Finally, the model that includes cooling and synthetic sigmoid rheological law shows good coherence for allthe cases except at Piton de la Fournaise. The model that aims to simulate the formation of a crust on thelava flow surface, lava flowing underneath and break-out mechanisms leads to the thickening of the crust.Hence, break-out mechanism is not reproduced with VolcFlow.

Le nord-ouest des Alpes est un domaine intraplaque présentant de très faibles déformations. C'est pourquoi il paraît délicat de déduire la probabilité d'occurrence d'un séisme de taille lithosphérique (magnitude supérieure à 7) à partir des observations de microsismicité. De telles observations sont en effet des processus superficiels et présentent peu ou pas de lien avec des processus profonds de plus grande ampleur. L'objectif est de déterminer le potentiel sismique d'un secteur au nord-ouest des Alpes en étudiant le champ de contrainte résultant d'un chargement gravitaire. Seuls les objets de taille lithosphérique, i.e. de l'ordre de la centaine de kilomètres sont pris en compte. Un modèle de contraintes à l'échelle 360 km par 400 km par 230 km d'épaisseur, centré sur la subduction fossile des Alpes de l'ouest et s'étendant jusqu'au nord de Strasbourg, est établi. L'étude des structures du nord-ouest alpin montre l'importance de l'orogène alpin qui se retrouve, enparticulier, dans les variations de profondeur des interfaces de la lithosphère. Une étude du champ de contrainte dans le socle a permis d'identifier une rotation des contraintes principales horizontales avec l'axe des Alpes. Bien que la valeur absolue des contraintes principales n'ait pas pu être déterminée, un rapport de valeur relative est calculé. Le résultat de la modélisation montre l'importance de la rhéologie dans le cas d'un chargement gravitaire. Si une rhéologie élastique est prise en compte, les directions de contrainte calculées sont totalement différentes des observations. Par contre, l'utilisation d'une rhéologie élasto-plastique combinée à l'utilisation d'une géométrie réaliste des interfaces lithosphériques permet d'obtenir des directions de contraintes cohérentes avec les données. / The north-west of the Alps is an intraplate domain with very slow deformations. So, it seems difficult to determine the probability of occurrence of a lithospheric earthquake (magnitude greater than 7) from microseismic observations. Such observations are superficial processes with little relation to deeper and bigger ones. The aim is to determine the seismic potential of a lithospheric sector north-west of the Alps, studying the stress field generated by a gravity driven model. This model is 360 km by 400 km by 230 km deep, centered on the west alpine fossil subduction and going up to the north of Strasbourg. The study of the north-west alpine structures shows the importance of the alpine orogen which generates variations in depth of the lithospheric interfaces. A study of the stress field in the basement shows a variation of principal stress directions along the strike of the Alpine chain. Even if the absolute magnitude of stresses could not be determined a relative magnitude ratio is calculated. Results underline the importance of rheology for a gravity driven model. If an elastic rheology is modeled, calculated stress directions do not match observations. However, using an elasto-plastic rheology with a realistic geometry of the lithospheric interfaces, we can obtain stress directions coherent with the data.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-11-05T14:38:58Z No. of bitstreams: 1 JOSÉ CARLOS FERREIRA - TESE (PPGEP) 2011.pdf: 2583715 bytes, checksum: 354f3d59e0d3399d607fa4a93fbde40a (MD5) / Made available in DSpace on 2018-11-05T14:38:58Z (GMT). No. of bitstreams: 1 JOSÉ CARLOS FERREIRA - TESE (PPGEP) 2011.pdf: 2583715 bytes, checksum: 354f3d59e0d3399d607fa4a93fbde40a (MD5) Previous issue date: 2011-08-05 / Capes / O presente trabalho tem, como objetivo, propor um novo equipamento para obtenção do extrato de soja e desenvolver um novo produto alimentício elaborado com polpa de umbu, extrato de soja e rapadura, de alta qualidade protéica e energética, para suprir as carências nutritivas essenciais da população de baixa renda, principalmente para merenda escolar. O estudo foi dividido em quatro capítulos. No Capítulo 1 se avaliaram o processo de obtenção do extrato de soja com diferentes proporções de água:soja (1:8, 1:10 e 1:12), e o preparo da umbuzada com diferentes concentrações de polpa de umbu (30, 40 e 50%). Avaliaram-se também as características físico-químicas (proteínas, carboidratos, lipídios, pH, acidez total titulável, cinzas, teor de água e valor calórico), termofísicas (condutividades térmica, difusividade térmica, massa específica e calor específico), as propriedades sensoriais (cor, aroma e sabor) do extrato de soja, polpa de umbu e das formulações de umbuzada. No Capítulo 2 estudou-se o comportamento reológico (10, 20, 30 e 40 oC) do extrato de soja, da polpa de umbu e das formulações da umbuzada e se avaliou dentre os modelos de Ostwald-de-Waelle e Casson qual apresentava o comportamento reológico. No Capítulo 3 foram estudadas a cinética de congelamento e o efeito das condições de congelamento sobre as características físico-químicas, sensoriais e microbiológicas das formulações de umbuzada. Ademais, avaliaram-se as formulações da umbuzada em condições de armazenamento nas temperaturas de (-20 oC, a -170 oC até -50 oC em vapor de nitrogênio líquido e a -196 oC até - 50 oC por imersão em nitrogênio líquido). No Capítulo 4 estudou-se a cinética de secagem por liofilização das formulações de umbuzada congeladas em três condições (-20 oC e até -50 oC em vapor e por imersão em nitrogênio líquido) e se avaliou dentre os modelos de Cavalcanti Mata, Page e Midilli, qual representa o comportamento das curvas de secagem com precisão e se quantificou o efeito das temperaturas de congelamento e do percentual de polpa de umbu nas características físico-químicas e sensoriais da umbuzada liofilizada. Com base nos resultados obtidos verificou-se que o extrato de soja na proporção soja:água de 1:8 apresentou as melhores características físicoquímicas e sensoriais. A condutividade térmica e a difusividade térmica diminuem e a massa específica aumenta com a elevação da concentração de polpa de umbu. Os modelos de Ostwalt-de-waelle e Casson foram, de maneira geral, os que melhor representaram o comportamento reológico do extrato de soja, da polpa de umbu e das formulações nas temperaturas estudadas. O congelamento até -50 oC por imersão em nitrogênio líquido, apresentou o menor tempo de congelamento. A difusividade efetiva média aumentou de acordo com a ordem do método de congelamento apresentada: -20 oC, a 50 oC em vapor de nitrogênio e a 50 oC por imersão em nitrogênio líquido. A formulação com 50% de polpa de umbu apresentou a maior taxa de secagem por liofilização e o modelo de Cavalcanti Matta foi o que melhor representou o comportamento das curvas de secagem por liofilização. / The present work has the aim to propose a new device to get the soybean extract and develop a new food product made with umbu pulp, soymilk and brown sugar, highquality protein and energetic, to supply the main nutritional needs of low-income population, especially for school lunches. The study was divided into four chapters. In Chapter 1 we evaluated the process of obtaining the soybean extract with different proportions of water: soybean (1:8, 1:10 and 1:12), the preparation of umbuzada with different concentrations of umbu pulp (30, 40 and 50%). Still, we evaluated the physico-chemical characteristic (protein, carbohydrates, lipids, pH, total acidity, ash, moisture content and calorific value), thermophysical (thermal conductivity, thermal diffusivity, density and specific heat), the sensory properties (color aroma and flavor) of soymilk, umbu’s pulp, umbuzada’s formulations. In Chapter 2 we studied the Rheological behavior (10, 20, 30 and 40 °C) of the soymilk of umbu’s pulp and umbuzada’s formulations and it was evaluated from the model Ostwald-Waelle and Casson which represented the rheological behavior. In Chapter 3 we studied the freezing kinetics and the effect of freezing conditions on the physico-chemical characteristic, sensory and microbiological umbuzada’s formulations. Moreover, the formulations were evaluated in the umbuzada storage conditions at temperatures of (-20 °C, the -170 °C to -50 °C in nitrogen steam liquid and -196 °C to -50 °C by immersion in liquid nitrogen). In Chapter 4, we studied the kinetics of drying by lyophilization umbuzada’s formulations frozen in three conditions (-20 °C and -50 °C in steam and immersion in liquid nitrogen), they were evaluated from the models Cavalcanti Mata, Page and Midilli which represents the behavior of the drying curves with precision, and quantified the effect of freezing temperatures and the percentage of umbu’s pulp in physico-chemical and sensory umbuzada lyophilized. Based on the results obtained the soy extract in proportion soybean: water 1:8 showed better physico-chemical and sensory. The thermal conductivity and thermal diffusivity decreases and density increases with concentration increasing of umbu’s pulp. Models Ostwalt-of-Waelle and Casson were, in general, those which better represent the behavior rheology of the soy extract, the umbu’s formulations and temperatures studied. Freezing to -50 °C by immersion in liquid nitrogen had the lowest freezing time. The average effective diffusivity increased according to the order of presented freezing method: -20 °C to 50 °C in nitrogen steam and 50 °C by immersion in liquid nitrogen. The formulation with 50% umbu’s pulp show the highest rate of drying by lyophilization and Cavalcanti Mata model was the one that best represented the behavior of drying curves by lyophilization.

La calcite (carbonate de calcium) est un matériau extrêmement répandu dans les roches telles que le marbre et comme constituant dans des domaines variés (bâtiment, pharmacie, papier, art). La compréhension des propriétés mécaniques des suspensions de calcite constitue une étape importante pour améliorer à la fois leur maniabilité ainsi que les propriétés finales du matériau fabriqué. Cette étude relie les propriétés rhéologiques (élasticité, écoulement) de ces suspensions à leurs interactions microscopiques. Les interactions attractives entre particules de calcite confèrent aux pâtes les propriétés de gels colloidaux caractérisés par un module élastique et une déformation critique, et ce pour une large gamme de concentrations. L'étude de ces grandeurs en fonction de la concentration a permis de mettre en évidence pour la première fois l'existence de deux régimes de déformation (liens forts et faibles) prédits théoriquement et de caractériser la dimension fractale. L'étude des interactions a été réalisée grâce à la mesure du potentiel Zeta des pâtes, du pH et au calcul de la longueur de Debye résultant de la force ionique. L'ajout d'additifs tels que la chaux ou la soude modifie les interactions. La chaux réduit fortement l'élasticité initiale des pâtes, facilitant leur maniabilité et renforçant la réactivité de la pâte en présence de CO2. L'ajout de soude augmente fortement l'attraction entre les particules ce qui se traduit à l'échelle macroscopique par l'existence de bandes de cisaillement. Cette manifestation de l'attraction entre colloïdes à l'échelle macroscopique avait été observée dans des émulsions concentrées mais encore jamais dans les gels colloïdaux / Calcite (calcium carbonate) is an extremely widespread material that can be found naturally in rocks (i.e. marble, limestone) and is employed in many industrial fields such as paper filling, pharmaceutical, art or construction. Understanding the mechanical properties of calcite suspensions is a first step to improve the workability of the paste as well as the final properties of solid mineral materials. Macroscopic characterization of calcite suspensions via rheological measurements are linked to microscopic interactions, via DLVO analysis. Our calcite pastes are weakly attractive systems showing a typical colloidal gel behavior and characterized by an elastic shear modulus and a critical strain. The elastic domain of pure calcite suspensions is characterized for a wide range of volume concentrations. The deformation at the end of linearity exhibits a minimum versus concentration, a major prediction of colloidal gel theory, never verified so far. The interaction forces between particles are tuned by addition of simple ionic species. Rheological measurements are analyzed through DLVO calculations, obtained by chemical speciations and ζ potential measurements on dense suspensions. Addition of calcium hydroxide improves initially the workability of the paste, enhancing the reactivity when in contact with CO2. The role of interaction forces is also evaluated with flow measurements. The addition of sodium hydroxide increases strongly the attraction between particles, inducing shear bands at the macroscopic scale. This correlation is well known for emulsions but never verified so far for colloidal gels

Ces travaux de thèse, financés par la société TERREAL (convention CIFRE), ont pour objectif de modéliser l’étape de façonnage des tuiles en terre cuite. La mise en forme des tuiles est à l’origine d’un tiers du rebus. Les attentes industrielles autour de ce sujet sont doubles : comprendre les phénomènes générant les défauts et mettre en place un outil de simulation numérique permettant de prévoir l’influence des paramètres produits / procédés sur l’apparition des défauts. La démarche scientifique s’est orientée autour de trois axes : la modélisation du comportement rhéologique, l’identification du comportement aux interfaces, la détermination d’un critère de fissuration et des mécanismes générant les défauts. Le modèle rhéologique est déterminé par analyse inverse d’essais de compression libre. Des essais complémentaires (cisaillement, flexion,…) ont été réalisés pour étudier plus finement le comportement du matériau. Des mesures de champs de déformation par stéréo corrélation ont permis de valider les modèles numériques de ces essais. Des mesures effectuées avec un tribomètre rectiligne ont permis de déterminer des modèles de frottement aux différentes interfaces du procédé (argile/acier ; argile/caoutchouc ; caoutchouc/résine). Quatre critères de fissuration ont été étudiés. Un critère en cisaillement maximum s’est montré le plus pertinent pour modéliser l’initiation des fissures. Des essais de façonnage sur des géométries partielles de tuiles ont permis de valider les différents modèles de comportement identifiés et de comparer deux technologies d’outillage (rigide et déformable). La simulation numérique 3D a permis de prédire la majorité des défauts liés aux écoulements. / This PhD study was supported by the company TERREAL. The aim is to model the forming step of clay tiles. The industrial expectations around this topic were double: understand the phenomena leading to defect occurence and to put in place a numerical simulation tool which allows to predict the influence of the product / process variations. The scientific approach turned around three axes: the determination of the constitutive model of the clay paste, the identification of the behavior at the different interfaces, the determination of a damage criterion and the mechanisms which generate defects. The different parameters of the constitutive law were identified by an inverse analysis of compression tests. Some additional tests (shearing test, bending test,…) were performed to investigate more precisely the material behavior. Kinematic full-field measurements by 3D digital image correlation allowed to validate the numerical model of these tests. Measurements with a rectilinear tribometer were carried out to identify a model of friction for the different interfaces involved in the process (clay/steel; clay/rubber and rubber/resin). Four cracking criteria have been studied. A maximum shear stress criterion proved to be the most relevant to assess the initiation of cracks. Forming tests of partial geometries of tiles allowed to validate the different behavior models identified and to compare two dies technologies (rigid dies and deformable dies). 3D numerical simulation allowed to predict the most of the defects related to the clay paste flow.

Les microorganismes présentent des comportements collectifs qui émergent des interactions qui se produisent à l’échelle individuelle. Dans le cas des suspensions concentrées (fraction volumique > 50%) les effets stériques deviennent dominants. C’est le cas du sperme de bélier sur lequel cette étude a principalement porté. Nous avons étudié certains aspects hydrodynamiques liés à la rhéologie du sperme et à la rhéotaxie. Nous montrons un comportement rhéo-fluidifiant en loi de puissance du liquide séminal reproductible d’un in- dividu à l’autre. Nous avons aussi mis en évidence qu’un contrôle chimique peut fortement affecter le comportement rhéotactique des spermatozoı̈des chez l’ovin et chez l’homme. Nous avons par ailleurs étudié la dynamique collective de la semence confinée dans des chambres d’épaisseur contrôlée en apportant des éclaircissements sur l’origine et la caractérisation du comportement turbulent observé. Nos résultats montrent que certaines caractéristiques de la turbulence bidimensionnelle se manifestent (loi de puissance du spectre d’énergie des vitesses, loi de séparation des traceurs passifs) que nous interprétons comme résultant d’une stratification laminée de l’écoulement par les interactions stériques à forte concentration. Enfin, nous avons développé et breveté un système micro-fluidique dans lequel une mise en rotation spontanée de la semence apparaı̂t. Nous avons analysé ce phénomène et l’avons relié à une transition de phase d’orientation cohérente avec une modélisation de type Self-Organized-Hydrodynamics. De plus nos résultats montrent une bonne corrélation entre la vitesse de rotation et la note de mobilité massale, donnant des perspectives d’applications pour la prédiction de la fertilité à ce dispositif. / Microorganisms exhibit collective behaviors that emerge from interactions occurring at the individual scale. In the case of high concentrated suspensions (volume fraction > 50%) steric effects become dominant. This is the case of ram semen on which this study focused. We first studied some hydrodynamic aspects related to the semen rheology and rheotaxis. We show a reproducible seminal plasma power law shear-thinning behavior from one subject to another. We have also highlighted that a chemical control can strongly affect the rheotactic behavior of sperms in the ovine and humans. We also studied the collective dynamics of the semen in chambers of control depth by providing clarification on the origin and characterization of the observed turbulent behavior. Our results show that some characteristics of two-dimensional turbulence occur (power law of the velocity energy spectrum, the pair-particles separation law ) that we interpret as the result of a stratification laminated flow induced by steric interactions at high concentration. Finally, we have developed and patented a micro-fluidic system in which a spontaneous spin-up appears. We analyzed this phenomenon and we connect it to a coherent orientation phase transition with a Self-Organized-Hydrodynamics modeling. In addition, our results show a good correlation between the speed and scoring of mass mobility, giving opportunities for application of the prediction of fertility for this device.

Dans les procédés liés aux émulsions, des écoulements turbulents et polyphasiques entrent en jeu. De tels procédés apparaissent dans des domaines variés. Dans l'industrie agro-alimentaire, la production de lait fait intervenir un homogénéisateur à haute pression, et certains produits tels que la mayonnaise sont des émulsions stables. On trouve aussi des émulsions dans le domaine de la santé : elles assurent le bon fonctionnement de nos poumons, tandis que d'autres peuvent être injectées par voie parentérale en tant que médicaments. On les retrouve aussi dans les procédés de séparation, par exemple eau-brut de pétrole dans l'industrie pétrochimique. Dans tous les cas, la fragmentation et la coalescence des bulles et gouttes doivent être maîtrisées, car elles influencent directement la distribution en taille de la phase dispersée. La fréquence d'apparition de ces phénomènes peut être prédite en utilisant des modèles adaptés. Cependant, la présence de molécules tensioactives modifie grandement cette fréquence et par conséquent la distribution en taille en sortie du procédé. Or, ce type de molécules est présent dans quasiment tous les procédés polyphasiques. L'étude des effets des tensioactifs dans ces procédés s'est alors imposée. Dans un des plus récents modèles, les bulles ou gouttes sont considérées comme des oscillateurs forcés par la turbulence de l'écoulement environnant. Il est alors nécessaire de connaître à la fois la turbulence dans le voisinage de la goutte et les propriétés dynamique de la goutte. La première peut être déterminée expérimentalement. La réponse de la goutte au forçage est alors décrite comme une somme d'harmoniques sphériques dont la dynamique est décrite pour chaque mode par une pulsation et un coefficient d'amortissement. Cette thèse aborde l’étude des effets des tensioactifs sur ces deux grandeurs. Elle s’est déroulée en collaboration entre l'IMFT et le LGC, ce qui a permis d'associer les compétences de chaque laboratoire dans les domaines de la physico-chimie, de l'hydrodynamique des phases dispersées et des écoulements turbulents diphasiques. Le projet lors de cette thèse est d'étudier numériquement les effets des tensioactifs sur les échelles temporelles caractéristiques des oscillations, dans le cas où la goutte est immobile ou bien en mouvement dans un fluide externe. Une équation de transport des tensioactifs ainsi que l'effet Marangoni à l'interface ont été modelisés dans le code DIVA, et validés à l'aide de cas tests. Ensuite, des simulations de gouttes subissant des oscillations de forme suivant le mode 2 des harmoniques sphériques ont permis de décrire les effets des tensioactifs sur la dynamique des interfaces. Ils ont été validés par la théorie pour des oscillations linéaires. Le couplage entre le mouvement d'ascension et les oscillations de formes a aussi été étudié, afin de comprendre l'effet d'un fort effet Marangoni, généré par l'ascension de la goutte, sur les oscillations. Les viscosités de surface peuvent aussi influencer radicalement la dynamique interfaciale. Lors de cette thèse, une méthode a été développée et validée pour permettre à l'outil de simulation de prendre en compte des viscosités de surface en se basant sur le modèle de Boussinesq-Scriven. Leur effet sur la dynamique des oscillations de forme a été étudié. / In many industrial processes, such as high-pressure homogenisation or water-oil separation, turbulent and multiphase flows are involved. To optimize those processes, coalescence and fragmentation need to be controlled since they impact directly the size distribution of drops and bubbles. The occurrence of those phenomena can be predicted using adapted models. However, the presence of surfactant molecules at the interface between two fluid phases can change radically the phenomenology of drops break up and coalescence, and their effect has not been properly included in existing models yet. In one of the latest models, drops are considered as forced oscillators driven by the local turbulence of a flow. It is therefore required to know the local turbulence of the flow and the dynamic properties of the drop. It is possible to measure experimentally the local velocities in a flow to determine the local average turbulent Weber number, which represents the forcing term of the oscillator. The dynamic response of the drop is described as a series of oscillators, the principal mode of which is characterized by two time scales, the pulsation and damping coefficient. The goal of this PhD is to study numerically the impact of surfactants on the two time scales mentioned above, whether the drop is still or in motion in the surrounding fluid. An equation of transport of surfactants and the Marangoni effect at the interface have been implemented in the code, and validated. Simulations of a drop undergoing shape oscillations along its eigenmode n = 2 have allowed to study the effects of surfactants on the time scales of oscillations, which were validated with theoretical predictions for linear oscillations. Surface viscosities can also influence the time scales of oscillations. Therefore, a numerical method has been developped and validated to take surface viscosities into account. The stress jump is based on the expression of the Boussinesq-Scriven model. Their effect is studied on the dynamic of oscillations.

Apesar do grande número de pessoas afetadas pela deficiência da enzima lactase, produtos destituídos de lactose, como as sobremesas à base de soja, ainda correspondem a um mercado pouco explorado pelas indústrias de alimentos e que requer inovações. Além disso, a quantidade de informações encontradas na literatura a respeito desse tipo de alimento é escassa. O desenvolvimento de sobremesas com derivados da soja é uma alternativa, não só para os consumidores que buscam produtos sem lactose, mas também para quem busca alimentos sem colesterol e com proteínas vegetais de alto valor biológico. Neste contexto, o presente trabalho teve como metas iniciais o desenvolvimento de sobremesas à base de soja enriquecidas com polpa de fruta, a caracterização desses produtos, e a correlação das suas propriedades (instrumentais x instrumentais e instrumentais x sensoriais) com o propósito de diminuir custos durante o desenvolvimento desse tipo de alimento. Para tanto, estudou-se, primeiramente, o efeito da adição de ingredientes importantes como a polpa de goiaba, o extrato de soja e o amido em diferentes concentrações nas formulações através de um planejamento fatorial 23. Essas formulações foram caracterizadas em relação ao pH, conteúdo de sólidos solúveis (CSS), capacidade de retenção de água (CRA), índice de sedimentação, microestrutura, reologia e cor. As características sensoriais das sobremesas também foram avaliadas por meio de Análise Descritiva Quantitativa (ADQ) com equipe treinada e através de testes de aceitação com mais de 50 provadores não-treinados. De acordo com a análise estatística (p < 0.05), as variáveis estudadas e suas interações, na faixa observada, influenciaram os parâmetros analisados. As sobremesas apresentaram teor de sólidos solúveis entre 17 e 23, pH entre 4,8 e 5,4 e valores de CRA medidos a 25 °C entre 68 % e 99 %; vale ressaltar que nenhuma das amostras apresentou sinerese após 120 horas de armazenamento a 25 °C. A partir de medições reológicas, verificou-se que os produtos apresentaram comportamento pseudoplástico sem resposta tixotrópica com características viscoelásticas de gel fraco (G' / G" < 3). As características microscópicas das sobremesas pareceram ser fortemente afetadas pelos componentes em estudo. Além disso, foi identificada uma correlação entre a CRA das amostras e parâmetros reológicos. Os atributos treinados na ADQ foram: cor rosa, consistência, sabor de soja, sabor goiaba e cremosidade. A cor das amostras verificadas por ADQ mostrou forte correlação com os parâmetros de cor L* (luminosidade) e hab (ângulo de hue). Além disso, algumas propriedades reológicas mostraram boa correlação com as propriedades sensoriais denominadas consistência (resistência ao fluir da colher) e cremosidade (percepção de consistência macia na boca). Ambos os módulos (elástico e viscoso) e o parâmetro n," que caracteriza a dependência do módulo viscoso com a frequência, podem ser índices úteis de textura sensorial para as sobremesas em estudo. Após essa etapa, foram feitos estudos específicos com o intuito de avaliar o efeito de novas variáveis de processo nas características da amostra. Nesse contexto, foi escolhida uma formulação para avaliar o efeito da substituição da carragena pela mucilagem da chia, considerada um espessante alimentar inovador. Novamente, as formulações foram caracterizadas quanto às propriedades reológicas, CSS, pH, cor e perfil sensorial. Os resultados mostraram que as amostras não diferiram quanto aos valores de pH, CSS e coordenada cromática a*. Quanto aos outros parâmetros de cor e reológicos, foram detectadas diferenças significativas entre as amostras, o que mostra a influência do tipo de espessante nestas características. Os resultados da ADQ evidenciaram que as amostras não apresentaram diferenças estatísticas quanto aos atributos, cor rosa, sabor de goiaba, sabor de soja e cremosidade, porém diferiram quanto à consistência. Logo, a adição da mucilagem de chia pode ser Nesse contexto, foi escolhida uma formulação para avaliar o efeito da substituição da carragena pela mucilagem da chia, considerada um espessante alimentar inovador. Novamente, as formulações foram caracterizadas quanto às propriedades reológicas, CSS, pH, cor e perfil sensorial. Os resultados mostraram que as amostras não diferiram quanto aos valores de pH, CSS e coordenada cromática a*. Quanto aos outros parâmetros de cor e reológicos, foram detectadas diferenças significativas entre as amostras, o que mostra a influência do tipo de espessante nestas características. Os resultados da ADQ evidenciaram que as amostras não apresentaram diferenças estatísticas quanto aos atributos, cor rosa, sabor de goiaba, sabor de soja e cremosidade, porém diferiram quanto à consistência. Logo, a adição da mucilagem de chia pode ser feita sem causar grandes modificações ao produto. Além disso, foi avaliado o efeito do uso do ultrassom, que é considerado uma tecnologia emergente, em uma das sobremesas desenvolvidas. As amostras foram tratadas com uma sonda de ultrassom durante 1, 3 e 5 minutos e, periodicamente, propriedades reológicas, pH, CSS, cor, tamanho de partícula e CRA foram monitorados durante 60 dias. As amostras sonicadas apresentaram menor tamanho médio de partícula, índice de consistência mais baixo, maior índice de fluxo e diferenças microestruturais consideráveis. No entanto, a capacidade de retenção de água e o índice de dispersão de tamanho de partícula não diferiram entre as amostras não tratada e tratadas durante 1 e 3 minutos; e nenhum dos tratamentos causou diferenças de cor visíveis entre as amostras. Após 60 dias de estocagem sob refrigeração, todas as propriedades avaliadas diferiram significativamente, com exceção do pH. A parte final do trabalho refere-se ao estudo de interações entre importantes componentes da formulação, como os polissacarídeos, carragena e carboximetilcelulose, e as proteínas presentes no extrato de soja. Para tanto, investigou-se a influência do pH (2-7) e da proporção de extrato de soja-polissacarídeo (5:1, 10:1, 20:1 e 40:1) em soluções aquosas com e sem polidextrose (10 %) como co-soluto. As interações entre os componentes foram estudadas através das análises de potencial zeta, medidas espectrofotométricas da interação entre azul de metileno e polissacarídeo, perfil de solubilidade da proteína, calorimetria diferencial de varredura, espectroscopia de infravermelho, difração de Raio-X, microscopia eletrônica de varredura e microscopia confocal de varredura a laser. Apesar das misturas estudadas apresentarem dependência com o pH e com a razão proteína-polissacarídeo, elas não apresentaram o mesmo comportamento. A presença de ambos os polissacarídeos modificou o perfil de solubilidade da proteína de soja, visto que diminuindo a razão extrato de soja-polissacarídeo, a formação de coacervados foi deslocada para uma região de pH mais baixo. As amostras também apresentaram diferenças consideráveis em relação aos seus termogramas, espectros de infravermelho e microscopias. A formação de complexos também foi detectada em regiões de pH em que ambos os biopolímeros estavam carregados negativamente. A influência da polidextrose foi detectada nas medidas espectrofotométricas com azul de metileno e nas imagens da microscopia confocal. Por fim, pode-se dizer que todas as variáveis de processo estudadas, como a concentração de ingredientes, a mucilagem da chia e o ultrassom, foram determinantes nas propriedades das amostras; e que os resultados obtidos provêm informações de uso prático para a indústria de alimentos, no que diz respeito ao desenvolvimento de formulações e controle e monitoramento de processos. Além disso, antes de elaborar novas formulações, é necessário verificar as interações entre os biopolímeros envolvidos, visto que dependendo da natureza dos componentes e das propriedades do meio, diferentes propriedades, como solubilidade, estabilidade e textura podem ser modificados. / Despite of the large number of people affected by lactase deficiency, lactose free products, such as soy-based desserts, still represent an unexplored market for the food industry, ie, a niche that requires innovations. Furthermore, the literature regarding the amount of information about this type of food is scarce. The development of desserts with soy is an alternative, not only for consumers who seek products without lactose, but also for those seeking foods without cholesterol and with vegetable proteins of high biological value. In this context, the goals of this research were to develop soy-based desserts enriched with fruit pulp, to characterize these products and to correlate properties (instrumental by instrumental and instrumental by sensory) in order to cut costs during the development of this type of product. Therefore, firstly, it was studied the effect of the addition of important ingredients like guava pulp, soy extract in different concentrations and starch in the formulations using a 23 factorial design. These formulations were evaluated as to pH, soluble solids content, water holding capacity (WHC), creaming test, microscopy, color and rheology. The sensory characteristics of the desserts were evaluated by Quantitative Descriptive Analysis (QDA) with trained panel and through acceptance testing with over 50 tasters. The statistical analysis showed that the studied variables and its interactions, in the observed range, influenced the analysed parameters. The desserts presented soluble solids from 17 to 23, pH between 4,8 and 5,4 and WHC values measured at 25 ° C between 68 % and 99 %, however, none of the samples showed syneresis after 120 hours of storage at 25 °C. From rheological measurements, it was verified that the products presented pseudoplastic behavior without thixotropic response and characteristics of weak gel (G’/ G” < 3). The microstructure of the produced desserts was found to be strongly affected by the components under study. Besides, an intimate correlation between WHC and rheology was identified. The raised attributes in QDA were pink color, consistency, soy flavor, guava flavor and creaminess. Color of the samples by QDA had high correlation with the color parameters regarding to luminosity (L*) and hue (h*). Furthermore, many rheological properties were well correlated with sensory properties referred to consistency (resistance to flow off the spoon) and creaminess (perception of soft consistency in the mouth). Both modules (storage and loss) and n” parameter which characterizes the frequency dependence of the loss modulus can be useful indices of sensory texture to desserts of this study. After this step, different studies have been made in order to evaluate the effect of new process variables on the sample characteristics. In this context, a formulation was chosen to evaluate the effect of the substitution of carrageen by chia mucilage that is considered a novel food thickener. Again, the formulations were characterized for their rheological properties, °Brix, pH, color and sensory profile by QDA. The results regarding to pH, ° Brix and color coordinate a* did not differ. Unlike these parameters, the other chromaticity coordinates and the rheological properties presented significant statistical differences between the samples. The QDA results showed that the samples did not differ as to the attributes, color, pink guava flavor, creaminess and flavor of soy, but differed in consistency. Thus, the addition of mucilage chia can be made without causing major changes to the product. Moreover, it was evaluated the effect of the use of ultrasound, which is considered an emerging technology, in one of the developed desserts. The samples were treated with an ultrasound probe for 1, 3 and 5 minutes and were monitored during storage under refrigeration (60 days). The treated samples showed lower mean particle size, lower consistency index, higher flow index and clear difference in their microstructure. However, water holding capacity and particle size dispersion index values did not differ among untreated and treated soy based desserts for 1 and 3 minutes and none of the treatments caused visible color differences among the samples. Periodically, rheological properties, pH, soluble solids content, color, particle size and water holding capacity were determined. After 60 days, all evaluated properties differ significantly, except the pH. The final work refers to the study of interactions between important components of the formulation, such as carrageenan, carboxymethylcellulose and soy proteins present in the soy extract. To this end, the influence of pH (2-7) and soy extract-polysaccharide ratio (5:1, 10:1, 20:1 and 40:1) were investigated in aqueous solutions with 10 % of polydextrose and without polydextrose by examining, methylene blue–polysaccharide interactions, pH-solubility profile of protein, -potential, differential scanning calorimetry, Fourier transform infrared spectroscopy, wide angle X-ray diffraction, scanning electron microscopy and confocal laser scanning microscopy (CLSM). Although both systems showed dependency on the pH and ratio, they did not present the same behavior. The presence of both polysaccharides modified the pH-solubility profile of soy protein and the pH range of complex formation shifted to a lower pH region decreasing the soy extract-polysaccharide ratio. The samples also presented detectable differences regarding to DSC, FTIR and microscopy analysis. The complex formation was also detected even in a pH region where both biopolymers were net-negatively charged. The influence of polydextrose was mainly detected by blue–polysaccharide interactions measures and CLSM-images. Finally, it can be concluded that all the process variables such as the concentration of ingredintes, chia mucilage, and ultrasound have altered the properties of the samples and the results can be used as tools to develop new formulations and to monitor processes. In addition, before developing new formulations, it is necessary to verify the interactions between biopolymers, since depending on the nature of the components and properties of the medium, different properties, such as solubility, stability and texture can be modified.

Magnetic resonance (MR) is a highly versatile technique with great potential for use in industrial applications; from the in situ study of unit operations to the optimisation of product properties. This thesis, concerned with the latter, is divided into two parts. Firstly, dynamic MR is applied to characterise the flow behaviour, or rheology, of process fluids. Such characterisation is typically performed using conventional rheometry methods operating offline, with an online, or inline, method sought for process control and optimisation. Until recently, MR was an unlikely choice for this application due to the requirement of high-field MR hardware. However, recent developments in low-field MR hardware mean that the potential of MR in such applications can now be realised. Since the implementation of MR flow imaging is challenging on low-field MR hardware, two new approaches to MR rheometry are described using pulsed field gradient (PFG) MR. A cumulant analysis of the PFG MR signal is first used to characterise the rheology of model power-law fluids, namely xanthan gum-in-water solutions, accurate to within 5% of conventional rheometry, the data being acquired in only 6% of the time required when using MR flow imaging. The second approach utilises a Bayesian analysis of the PFG MR signal to characterise the rheology of model Herschel--Bulkley fluids, namely Carbopol 940-in-water solutions; data are acquired in only 12% of the time required for analysis using MR flow imaging. The suitability of the Bayesian MR approach to study process fluids is demonstrated through experimental study on an alumina-in-acetic acid slurry used by Johnson Matthey. Secondly, MR imaging is used to provide insights into the origins and mechanisms of colloidal gel collapse. Many industrial products are colloidal gels, a space-spanning network of attractive particles with a yield stress. Colloidal gels are, however, known to undergo gravitational collapse after a latency period, thus limiting the shelf-life of products. This remains poorly understood, with a more detailed understanding of both fundamental interest and practical importance. To this end, MR imaging is applied offline to investigate the phase behaviour of colloidal gels. In particular, a comparison of the simulated and experimental phase diagrams suggests gravitational gel collapse to be gravity-driven. Furthermore, measurement of the colloid volume fraction using MR imaging indicates the formation of clusters of colloids at the top of the samples. Whether such clusters initiate gravitational gel collapse is yield stress-dependent; the gravitational stress exerted by a cluster must be sufficient to yield the colloidal gel.