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Tavakoli, Gheynani Touraj. "Hydrodynamique et transfert gaz-liquide non newtonien en fluidisation triphasique." Toulouse, INPT, 1989. http://www.theses.fr/1989INPT039G.
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La fluidisation gaz-liquide-solide est etudiee experimentalement du point de vue hydrodynamique (vitesse minimale, expansion, retentions du liquide et du gaz) et du point de vue transfert de matiere par absorption d'oxygene. Les mesures hydrodynamiques sont effectuees avec divers liquides newtoniens et non newtoniens et par analogie on determine une viscosite apparente. Par rapport a l'eau, l'ecoulement est profondement modifie par la coalescence qui produit un regime a bulles deformees ou a bouchons. Cependant, les retentions sont assez peu influencees par la viscosite de meme que par le diametre des particules. En transfert de matiere, les profils de concentration en oxygene dissous sont traites par le modele a dispersion axiale et fournissent les coefficients caracteristiques, de la dispersion axiale et du transfert volumetrique. L'accroissement de viscosite se traduit essentiellement par une forte reduction du coefficient volumetrique de transfert en raison de la reduction d'aire interfaciale. Par contre, l'influence de la vitesse de gaz reste tres importante. Le modele peut etre ameliore par la prise en compte de la coalescence, par l'intermediaire d'une reduction axiale exponentielle de ce coefficient volumetrique
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Ali, Adib Tarif. "Estimation et lois de variation du coefficient de transfert de chaleur surface / liquide en ébullition pour un liquide alimentaire dans un évaporateur à flot tombant." Paris, AgroParisTech, 2008. http://pastel.paristech.org/4544/01/2008AGPT0007.pdf.
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Le coefficient de transfert de chaleur est nécessaire pour concevoir et dimensionner un évaporateur utilisé pour concentrer un liquide, tel que rencontré couramment dans les industries alimentaires. Le coefficient de transfert de chaleur le plus variable et le plus incertain est du côté produit, entre paroi et liquide, noté « h ». Il varie à la fois avec les propriétés thermo-physiques du liquide traité (ηL, σL, λL, ρL, CpL, ω,. . . ) et avec les paramètres du procédés (type d’évaporateur, φ ou Δθ, Γ (δ), P, rugosité de la surface, encrassement, etc), ces grandeurs étant définies dans le texte. Mais h est aussi lié au régime d’ébullition (nucléée ou non nucléée), et pour les évaporateurs de type « flot tombant », au régime d’écoulement laminaire ou turbulent, selon le nombre de Reynolds en film Ref. Nous avons étudié le cas des évaporateurs « à flot tombant », très utilisés dans les industries alimentaires pour concentrer le lait et les produits laitiers, les jus sucrés, les jus de fruits et légumes. L’objectif de notre travail était de définir une méthode fiable et économique pour évaluer a priori le coefficient de transfert de chaleur h côté liquide en ébullition dans un évaporateur flot tombant. La première partie de la thèse a été consacrée à l’analyse bibliographique, qui a révélé une grande incertitude actuelle dans la prévision de h, sur la base des formules de la littérature, et des paramètres descripteurs proposés. La deuxième partie de la thèse a été de concevoir et construire un pilote utilisable pour estimer h, dans des conditions stationnaires connues et reproductibles. Dans la troisième partie, on présente les résultats et commente les lois de variations de h en fonction de la concentration de matière sèche du liquide XMS, de la température d’ébullition de liquide θL (ou P), du flux de chaleur φ ou Δθ, et du débit massique de liquide par unité de périmètre de tube Γ, pour des propriétés de surface de chauffe fixées (ici, paroi en acier inoxydable poli Rs≈0,8 μm). On commente l’effet sur h de chaque variable isolément, les autres étant maintenues constantes, ce qui confirme l’importance de la transition du régime non nucléé au régime nucléé, cette transition variant avec la nature du liquide, sa concentration, et le flux de chaleur. On a aussi montré la possibilité de modéliser un produit donné dans l’ensemble du domaine expérimental, où tous les paramètres peuvent varier simultanément, avec peu de coefficients, selon deux types d’équations (polynomiale et puissance). On a comparé le cas d’un liquide Newtonien (jus sucré) et non Newtonien (solution de CMC dans l’eau). On a aussi observé le débit de mouillage critique Γcri et ses lois de variation. On a aussi démontré la possibilité de simplifier le plan d’expérience, aussi bien pour les liquides Newtoniens que non Newtoniens, tout en gardant un coefficient de corrélation satisfaisant le domaine Γ > Γcri, cette modélisation pouvant servir de base de données produit pour l’ingénierieThe heat transfer coefficient value is necessary to calculate the eat exchange surface when designing an evaporator, as currently used to concentrate liquids in food industry. The boiling heat transfer coefficient on the liquid side (h) is the most uncertain and: it depends on the liquid thermo-physical properties (ηL, σL, λL, ρL, CpL, ω,. . . ) as well as on the process conditions (type of evaporator, φ ou Δθ, Γ (δ), P, surface roughness, fouling, etc). Also, h depends on the boiling regime (non-nucleate or nucleate) and on the flow regime (laminar or turbulent) according to the film Reynolds number in falling film evaporators. The objective of our work is to define an economical and robust method to estimate h in a falling film evaporator which is common in food industry for concentrating fruit juice, milk and sugar solutions. The first section of our study was a bibliographic analysis which revealed the important dispersion among the h values calculated from the formulas cited in literature The second section was to design and construct a laboratory scale falling film evaporator (pilot) used to estimate h at stationary parameters conditions. The third section was to describe the results and variation laws of h versus the liquid dry matter concentration XMS, the boiling temperature θL, the heat flux φ or temperature gap Δθ and mass flow rate per unit of perimeter length Γ (with describing the critical mass flow for some solutions) noted that the nature of heating surface is kept constant during our work. We described the effect of each variable separately on h where, the other variables being kept constant. Also we studied the transition from non nucleate regime, which varied with the nature of liquid and the liquid concentration. Finally, we presented the experimental models for h = f (XMS,θL,φ,Γ) for a Newtonian liquid (sugar solution) and non Newtonian solution (CMC) that may be used for industrial evaporator design after validation. We have also proposed a method for the simplification or the experimental design
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Ali-Adib, Tarif. "Estimation et lois de variation du coefficient de transfert de chaleur surface/ liquide en ébullition pour un liquide alimentaire dans un évaporateur à flot tombant." Phd thesis, AgroParisTech, 2008. http://pastel.archives-ouvertes.fr/pastel-00004544.
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Le coefficient de transfert de chaleur est nécessaire pour concevoir et dimensionner un évaporateur utilisé pour concentrer un liquide, tel que rencontré couramment dans les industries alimentaires. Le coefficient de transfert de chaleur le plus variable et le plus incertain est du coté produit, entre paroi et liquide, noté « h ». Il varie à la fois avec les propriétés thermo-physiques du liquide traité (ηL, σL, λL, ρL , CpL, ω, ...) et avec les paramètres du procédé (type d'évaporateur, φ ou Δθ, Γ (δ), P, rugosité de la surface, encrassement, etc), ces grandeurs étant définies dans le texte. Mais h est aussi lié au régime d'ébullition (nucléée ou non nucléée), et pour les évaporateurs de type « flot tombant », au régime d'écoulement laminaire ou turbulent, selon le nombre de Reynolds en film Ref. Nous avons étudié le cas des évaporateurs « à flot tombant », très utilisés dans les industries alimentaires pour concentrer le lait et les produits laitiers, les jus sucrés, les jus de fruits et légumes. L'objectif de notre travail était de définir une méthode fiable et économique pour évaluer a priori le coefficient de transfert de chaleur h coté liquide en ébullition, dans un évaporateur flot tombant. La première partie de la thèse a été consacrée à l'analyse bibliographique, qui a révélé une grande incertitude actuelle dans la prévision de h, sur la base des formules de la littérature, et des paramètres descripteurs proposés. La deuxième partie de la thèse a été de concevoir et construire un pilote utilisable pour estimer h, dans des conditions stationnaires connues et reproductibles. Dans la troisième partie, on présente les résultats et commente les lois de variations de h en fonction de la concentration de matière sèche du liquide XMS, de la température d'ébullition de liquide θL (ou P), du flux de chaleur φ ou (Δθ), et du débit massique de liquide par unité de périmètre de tube Γ, pour des propriétés de surface de chauffe fixées (ici, paroi en acier inoxydable poli Rs ≈ 0,8 μm). On commente l'effet sur h de chaque variable isolément, les autres étant maintenues constantes, ce qui confirme l'importance de la transition du régime non-nucléé au régime nucléé, cette transition variant avec la nature du liquide, sa concentration, et le flux de chaleur. On a montré la possibilité de modéliser un produit donné dans l'ensemble du domaine expérimental, où tous les paramètres peuvent varier simultanément, avec peu de coefficients, selon deux types d'équations (polynomiale et puissance). On a comparé le cas d'un liquide Newtonien (jus sucré) et non-Newtonien (solution de CMC dans l'eau). On a aussi observé le débit de mouillage critique Γcri et ses lois de variation. On a aussi démontré la possibilité de simplifier le plan d'expérience, aussi bien pour les liquides Newtoniens que non-Newtoniens, tout en gardant un coefficient de corrélation satisfaisant dans le domaine Γ > Γcri, cette modélisation pouvant servir de base de données produit pour l'ingénierie.
4
Hoareau, Frédéric. "Étude dynamique et thermique de suspensions solides-liquides non newtoniennes en conduite." Nancy 1, 1996. http://www.theses.fr/1996NAN10305.
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Dans le cadre d'un projet européen F. L. A. I. R. , l'étude du LEMTA-CNRS a porté sur un mélange de sphères dans des liquides newtoniens et non newtoniens de viscosités ou consistances variables. La géométrie d'écoulement se divise en un tube simple suivi d'une succession de convergents-élargissements brusques destines à brasser le fluide. Un élément chauffant en cuivre, identique à la géométrie, a permis de déterminer les coefficients d'échange liquide-sphère et les lois de transfert de chaleur paroi-mélange. Un film vidéo a été réalisé pour suivre le comportement des sphères baignant dans différentes concentrations non newtoniennes coulant dans le tube et la géométrie. Il montre l'accumulation de débris solides en aval de l'élargissement brusque pouvant conduire à l'encrassement dans le cas de fortes concentrations de sphères. Le second résultat montre l'apparition précoce de la turbulence dans la géométrie, à des nombres de Reynolds faibles (Re=200). Pour le tube, l'introduction de sphères accroit la perte de charge et renforce le caractère non newtonien du mélange. Une première campagne de mesure par vélocimétrie laser a donné le champ de vitesse dans la géométrie complexe. Une deuxième campagne mettant en œuvre la technique électrochimique, a permis l'identification des régimes d'écoulement diphasiques. Dans la géométrie, le gradient de vitesse pariétal est nettement accru pour les mélanges liquides non newtoniens-sphères. De même, on constate un accroissement du taux de fluctuation du gradient pariétal de vitesse. Les différentes solutions non-newtoniennes étudiées ont montré une étroite dépendance du gradient pariétal de vitesse avec les interactions particule-liquide, la viscosité du liquide suspendant limitant les propriétés diffusionnelles des sphères. Ceci a été confirmé par l'étude thermique.
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Napitupulu, Farel Hasiholan. "Mesures de la conductivité thermique de fluide non-newtonien à l'aide d'une sonde de mesure de type aiguille, basée sur une méthode thermique impulsionnelle : applications aux solutions aqueuses de polymères hydrosolubles et aux suspensions solide/liquide concentrées." Compiègne, 1988. http://www.theses.fr/1988COMPI278.
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La mesure des caractéristiques thermo physiques de produits fluides non-Newtoniens, en particulier leur conductivité thermique, revêt une grande importance pour le développement de procédés qui impliquent un traitement thermique (réchauffage, refroidissement, cuisson, etc. . . ). Elle permet par ailleurs, d'envisager un contrôle qualité de ces produits quand leurs caractéristiques thermo physiques se trouvent être suffisamment dépendante de leur formulation. Pour le cas de suspensions solide/liquide concentrées, la concentration massique, par exemple, est un paramètre de qualité fondamentale qui influence fortement non seulement les propriétés rhéologiques du produit, fortement dépendantes de la concentration, mais aussi peut constituer une méthode indirecte de contrôle d'une opération de mélange en continue, ou de contrôle de la stabilité sédimentaire par exemple. On présente une sonde thermique de type aiguille, basée sur une méthode thermique impulsionnelle susceptible de mesurer in situ la conductivité thermique apparente de solutions aqueuses de polymères hydrosolubles et de suspensions solide/liquide concentrées. Les variations de la conductivité thermique à 20°C en fonction de la concentration de la solution aqueuse, sont fournies pour trois CMC et un CARBOPOL disponibles commercialement, conférant à la solution des viscosités croissantes. On détermine également les variations de la conductivité thermique de ce type de solution en fonction de la température. En ce qui concerne les mélanges solide/liquide, les suspensions étudiées sont des mélanges pseudo-homogènes de charbon dans l'eau (" liquid coal slurry technology ") et de billes de polystyrène dans l'eau, à comportement rhéologique non-NewtonienThe measurement of the thermophysical properties of non-Newtonian fluids, particularly their thermal conductivity, is highly important for development of processes involving heat treatment (heating, coling, backing, etc. . . ). It also helps to plan the quality control of these products when their thermophysical properties are sufficiently dependent on their formulation. For the case of concentrated solid/liquid suspensions, the mass concentration, for example, is a fundamental quality parameter, which strongly influences not only the product's rheological properties, but also its economics value. The determination of the product's thermal conductivity, which is strongly dependent on concentration, could often an indirect control method of a continuous mixing operation, or, for example, a method to monitor the sedimentative stability. The author presents a needle-type thermal probe, based on the transient heat flow method (line-source technique), designed for the in situ measurement of the apparent thermal conductivity of aqueous solutions of water-soluble polymers and of concentrated solid/liquid suspensions. The thermal conductivity variations at 20°C, versus concentration of the aqueous solution, are given for three CMC and for one CARBOPOL, commercially available, given a large range of viscosity. The thermal conductivity variation versus temperature is also given. The suspension investigated is mixture of coal in water and polystyrene spheres in water. They consist in pseudo homogenous ùixture behaving as highly viscous non-Newtonian fluids
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Fyrippi, Irene. "Flowmetering of non-Newtonian liquids." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400185.
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Poole, Robert John. "Turbulent flow of Newtonian and non-Newtonian liquids through sudden expansions." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399176.
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Smith, Sarah Elizabeth. "Turbulent duct flow of non-Newtonian liquids." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399184.
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The turbulent flow of non-Newtonian fluids in straight ducts has been investigated. Specifically, the fully developed circular pipe flow, axisymmetric sudden expansion flow and fully developed square duct flow were studied. The pipe flow study analysed previous measurements of the mean velocity profiles and friction factor-Reynolds number characteristics of different non-Newtonian fluids in pipe fully developed pipe flows. An investigation of different nondimensional parameters permitted initial progress on developing a correlation between drag reduction and fluid rheology to be made. Comparison of the ranking orders of drag reduction, fluid extensional viscosity and fluid elasticity revealed that these fluid properties are most strongly correlated with drag reduction at low shear/strain rates (that is, in the buffer and outer regions of the boundary layer). The sudden expansion geometry was investigated for flows of aqueous Xanthan gum solution and two reference Newtonian fluids. A smooth contraction was placed at the inlet to the sudden expansion. Few significant differences were observed between the mean flow behaviours of the test fluids for the turbulent Reynolds numbers tested (26,000 and 80,000). These results may reflect the manner in which the rigid, rod-like molecules found in Xanthan gum influence the flow behaviour. Turbulence measurements indicated that all three turbulence components were suppressed for the polymer solution flow within the free shear layer downstream of the expansion. The turbulent flow of two non-Newtonian fluids (a blend ofXanthan gum and Carboxymethylcellulose in water and an aqueous solution of polyacrylamide) in a square duct were compared with a turbulent Newtonian square duct flow. Although suppression of the transverse turbulence components was noted, the polymer solutions also strongly affected the behaviour of the secondary flows found in turbulent non-circular duct flows of Newtonian fluids. Specifically, the secondary flows appeared to be weakened in the polymer blend flow and completely suppressed in the polyacrylamide solution flow. It is anticipated that fluid elasticity is influential in this suppression
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DUTRA, EDUARDO STEIN SOARES. "DISPLACEMENT OF NON-NEWTONIAN LIQUIDS IN ECCENTRIC ANNULI." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6947@1.
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PETRÓLEO BRASILEIRO S. A.Após a perfuração de poços de petróleo, a lama utilizada na remoção de cascalho, lubrificação e resfriamento da broca deve ser removida e substituída por uma mistura de cimento. Essa substituição se dá pelo deslocamento de um fluido por outro no espaço anular entre a formação rochosa e a coluna de completação ou revestimento. A mistura de cimento tem a função de garantir a estabilidade estrutural do poço evitando danos ambientais e prejuízos econômicos. Para melhores resultados do processo de cimentação, utilizam-se fluidos intermediários, também chamados de colchões lavadores e espaçadores, entre os fluidos principais. A boa qualidade do deslocamento dos fluidos pode ser avaliada pela forma da interface entre eles. Perfis mais acentuados sugerem um atravessamento indesejável do fluido deslocante (cimento) através do deslocado (fluido de perfuração). Por outro lado, perfis achatados indicam um deslocamento mais eficiente. Neste trabalho foi feita uma análise experimental e numérica do processo de cimentação, investigando a forma da interface e a eficiência do deslocamento dos fluidos. Uma planta experimental vertical foi construída, simulando um processo de deslocamento de fluidos em anulares excêntricos de poços. Com uma câmera digital CCD foram filmadas as interfaces entre os fluidos durante o escoamento e com essas imagens puderam-se comparar os resultados com as simulações numéricas realizadas num softw are comercial, usando o método de volumes finitos. Foram analisados os efeitos de diferentes parâmetros como a excentricidade, o regime de escoamento, e, principalmente o comportamento mecânico dos fluidos envolvidos (reologia) na eficiência do deslocamento. Com base nesses resultados é possível prever quais parâmetros operacionais otimizam o processo de deslocamento.
In cementing processes of oil wells, the mud formerly used to drag the gravel, to lubricate and to cool the drill is removed and substituted by a cement mixture. This substitution is obtained by the displacement of a fluid by another in the annulus between the rock formation and the casing. For best results of cementing process, intermediate fluids, also called spacers, are used between the drill mud and the cement mixture. The displacement process is very complex due to geometry and fluids characteristics. The annular space is eccentric in most cases, and both drilling mud and cement mixtures are non-Newtonian fluids. In this work, an experimental and numerical study is performed to analyze this process. A vertical experimental plant was constructed to simulate the fluid displacement through eccentric annuli. The interface shapes between two adjacent fluids were visualized using a digital CCD camera. The images were compared with the results obtained in the numerical simulations. The numerical solution was obtained via the Finite Volume technique and using the Volume-of-Fluid method. The effects of eccentricity, displacement velocity and rheological parameters on the displacement e± ciency were investigated. Based on these results we can predict the liquid characteristics and the operational parameters that optimize the displacement process.
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BAZZI, MARISA SCHMIDT. "BREAKUP DYNAMICS OF NON-NEWTONIAN THIN LIQUID SHEETS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=34574@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE EXCELENCIA ACADEMICA
BOLSA NOTA 10
Filmes finos de líquidos estão presentes em uma gama de aplicações industriais, como processos de atomização e revestimento de substrato. O processo de quebra pode ser divido em duas etapas: o estágio de ruptura, e o estágio de retração. O primeiro, movido pelas forças de van der Waals, ocorre quando uma pequena perturbação cresce e provoca o aparecimento de um pequeno furo no filme. O segundo, movido por forças capilares, provoca o crescimento desse furo levando à desintegração do filme de líquido. A estabilidade de uma cortina de líquido depende das características da perturbação, da espessura do filme e das propriedades do fluido. Análises experimentais mostraram que uma cortina super fina pode ser obtida pela utilização de fluidos viscoelásticos. Os mecanismos físicos associados à esta estabilidade, contudo, não são totalmente compreendidos. Este trabalho apresenta um estudo numérico e teórico dos efeitos das propriedades viscoelásticas na estabilidade de uma cortina de fluido, englobando ambos os estágio do processo. As análises numéricas foram desenvolvidas através da expansão assintótica das variáveis do escoamento com aplicação de um esquema de integração no tempo totalmente implícito. A partir da análise teórica da dinâmica de ruptura foi possível obter um critério de estabilidade linear para perturbações planares e axissimétricas em fluidos Newtonianos e não-Newtonianos. O tempo de ruptura e a velocidade de retração do filme foram calculados numericamente como função das propriedades viscoelásticas do líquido. Resultados mostraram que as forças elásticas atuam de forma a dificultar o processo de quebra e retração. Análises da evolução da espessura mostraram que as propriedades reológicas do fluído também interferem no formato que o filme de fluido assume durante o processo de retração. Para regimes de baixa viscosidade, as forças elásticas atuaram evitando a formação de ondas capilares observadas em fluidos Newtonianos.
Thin free liquid sheets are ubiquitous in many industrial processes, such as atomization and curtain coating. Liquid sheets are susceptible to instabilities at the interface, which can grow, triggering a breakup process. This process can be divided into two different stages: the rupture stage and retraction. The first, driven by van der Waals force, occurs when a small instability grows until it pinches-off the sheet. The second, driven by capillary forces, induces the growth of the hole caused by the pinch-off, leading to the full disintegration of the liquid sheet. The stability of a liquid sheet depends on disturbance characteristics, sheet thickness, and fluid properties. Experimental analyses have shown that thinner stable liquid curtain can be obtained with viscoelastic liquids. The underlyning physical mechanisms associated with increased stability are, however, not fully understood. This work presents a theoretical and numerical analysis of the effect of viscoelasticity on the stability of a thin liquid sheet during both stages of the breakup process. We first analyze the rupture dynamics, deriving linear stability criteria for both planar and axisymmetric perturbations of Newtonian and Oldroyd-B liquids. The time evolution of planar and axisymmetric perturbations in an Oldroyd-B liquid sheet is evaluated using the asymptotic expansion of the flow variables and a fully-implicit time integration scheme. The rupture time and retraction velocity are calculated as a function of the viscoelastic properties. The results show that the liquid rheological behavior does not influence the linear stability criterion. Nevertheless, it has a strong effect on the growth rate of the disturbance and retraction velocity, increasing, thus, the breakup time. The results show that elastic forces act to hinder the rupture and retraction stages. Analysis of the temporal evolution of the thickness profile reveals that liquid rheological behavior also affects the shape of the liquid sheet. For low viscosity regime, the elastic forces damp the capillary waves that arise during the retraction of Newtonian sheets.
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Cappello, Vincenzo. "Extrapolation des réacteurs agités gaz-liquide par modélisation tridimensionnelle de l'hydrodynamique, transferts et cinétique." Thesis, Université Clermont Auvergne (2017-2020), 2020. http://www.theses.fr/2020CLFAC040.
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Dans le cadre de la production de bio-carburants, les fermenteurs agités aérés sont utilisés la culture de micro-organismes car ils permettent d’assurer un bon transfert d’oxygène entre gaz et liquide, tout en homogénéisant de manière efficace la concentration en substrats. Dans le cas de la production d’enzyme par le champignon filamenteux Trichoderma reesei (une étape clef de la production d’éthanol 2G), le transfert d’oxygène est dégradé par la rhéologie non-newtonienne du moût fermentaire. Par ailleurs, les volumes fermentaires nécessaires aux futures unités de production de bioéthanol sont tellement élevés, de l’ordre de plusieurs centaines de m3 ou plus, que l’homogénéité des substrats n’est plus assurée.Dans ce contexte, la finalité des travaux présentés était de développer un outil de prédiction de performances et d’extrapolation des fermenteurs aérés, basé sur la mécanique des fluides numériques (ou CFD : Computational Fluid Dynamics), et permettant de coupler l’hydrodynamique, la rhéologie, le transfert de matière ainsi que le métabolisme simplifié des microorganismes. Pour arriver à cela, plusieurs étapes expérimentales ont été préalablement menées.Les tailles de bulles présentes dans divers milieux (filtrat fermentaire, milieux modèles) ont été caractérisées à l’aide d’une technique de sonde optique développée à IFPEN lors de travaux antérieurs, mais encore jamais appliquée aux milieux non-newtoniens. Ces mesures inédites de tailles de bulles ont été complétées par la caractérisation du transfert gaz/liquide (kLa) dans chaque système étudié, et la combinaison des différents résultats a permis de développer un modèle de coefficient de transfert (kL) à implémenter dans le modèle CFD. Par ailleurs, des caractérisations hydrodynamiques de type Temps de mélange (par colorimétrie et traitement d’image) et Vélocimétrie (par tube de Pavlov) ont été menées dans les milieux visqueux aérés pour valider les simulations hydrodynamiques.Le modèle développé, basé sur une approche diphasique Eulérienne, et une description moyennée des champs de vitesse (approche dite RANS : Reynolds Averaged Navier-Stokes équations) est utilisé pour illustrer la dégradation du mélange lors de l’extrapolation de la production d’enzymes. Ce phénomène se traduit par l’apparition de gradients de concentrations en substrats (sucres, oxygène dis- sous). Les résultats issus du modèle seront utilisés pour guider les futurs développements technologiques de fermenteurs, ainsi que pour mener des cultures biologiques représentatives de type scale-down, en fermenteurs multizones. Les simulations numériques et les expériences de scale-down permettront d’évaluer la résistance des microorganismes aux gradients de concentrations en substrats subis dans les fermenteurs industrielsMechanically-agitated reactors are widely used in aerobic fermentation, because they provide good mixing of reactants and high performance in terms of oxygen mass transfer. In the enzyme production process by filamentous fungi Trichoderma reesei, the mass transfer is hindered by the complex rheology of the fermentation broth. This process is a key step in the production of second-generation ethanol; however, because of the high fermentation volumes (∼ 100 m3) required for future bioethenol production units, the reactor scale-up is challenging. In fact, by increasing the size of the fermenter, large scale substrate gradients tend to appear.In this framework, the objective of this study is to develop a predictive tool based on Computational Fluid Dynamics (CFD) for the design and scale-up of aerated reactors. The numerical model here proposed, allows one to characterize such systems by coupling hydrodynamics, rheology, mass transfer, and a simplified metabolic model. To assess the fidelity of the model, several experimental analyses were carried out. Bubble size in shear-thinning liquids and in fermentation broth was measured thanks to a novel technique that was previously developed at IFPEN. This measuring techniques is based on phase- detective optical probes, and its use in stirred tank reactors and in viscous liquids was validated during this study. Bubble size measurements were supplemented with gas-liquid transfer coefficient (kLa) and gas holdup measurements. By combining these data, it was possible to develop a dimensional model for the liquid-side mass transfer coefficient (kL), that served to model the mass transfer mechanism in the CFD simulations.Moreover, the reactor hydrodynamics was characterized in terms of mixing time (via colorimetric method and image processing), and liquid velocity (with the Pavlov tube). These data were then used to quantify the accuracy of the simulations. The numerical model — based on the two-phase Eulerian model, and on Reynolds-averaged Navier-Stokes equations — was used to highlight the mixing degradation that accompanies the scale-up of the protein production process. Results from coupled simulations (distribution of substrate and oxygen concentrations) will be used to guide future design and technology optimization of fermenters, as well as to develop more representative scale-down models for microbial cultures. CFD simulations and scale-down data will assess the microorganisms’ resistance to exposure to substrate content variation inside industrial reactors
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Dressler, Daniel. "An experimental investigation of Newtonian and non-Newtonian spray interaction with a moving surface." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/71.
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As a logical extension of previous work conducted into viscoelastic atomization, initially motivated by the need to improve spray coating transfer efficiencies, an experimental investigation into the spray-surface interaction for a number of Newtonian and non-Newtonian substitute test liquids is presented. Three model elastic liquids of varying polymer molecular weight and three inelastic liquids of varying shear viscosity were sprayed upon a moving surface to isolate the effect of elasticity and shear viscosity, respectively, on spray impaction behavior. In addition, two liquids exhibiting shear thinning behavior and an industrial top of rail liquid friction modifier, KELTRACK, for use in the railroad industry, were included in the spray tests. High-speed photography was used to examine the impingement of these liquids on the surface.
Ligaments, formed as a consequence of a liquid’s viscoelasticity, were observed impacting the surface for 300K PEO, 1000K PEO, and KELTRACK. These ligaments were broadly classified into four groups, based on their structure. Splashing of elastic liquid ligaments and droplets led to filamentary structures being expelled from the droplet periphery, which were then carried away by the atomizing air jet, leading to reductions in transfer efficiency. The effect of increasing elasticity amongst the three varying molecular weight elastic solutions was shown to increase the splash threshold; a similar effect was noted with increasing shear viscosity.
Attempts were made at quantifying a critical splash-deposition limit for all test liquids however due to imaging system limitations, no quantitative conclusions could be made.
For KELTRACK, both droplets and ligaments spread and deposited on the rail surface upon impact, with no observed splash or rebound. Splash was only noted when droplets impinged directly on a previously deposited liquid film and even then, splashing was well contained. Thus, KELTRACK’s current rheological formulation proved to be very effective in ensuring high coating transfer efficiencies.
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Kanel, Jeffrey Scott. "Minimum impeller speeds and power requirements for complete dispersion of non-Newtonian liquid-liquid systems in baffled vessels." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/11256.
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Sai, Ramesh Prassanna. "Instability and Breakup of Non-Newtonian Viscoelastic Liquid Jets." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337717825.
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Zhdanov, Sergey. "Kinetics of spreading over porous substrate." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/33884.
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The spreading of small liquid drops over thin and thick porous layers (dry or saturated with the same liquid) has been investigated in the case of both complete wetting (silicone oils of different viscosities) and partial wetting (aqueous SDS solutions of different concentrations). Consideration has been carried out from both experimental and theoretical points of view. Nitrocellulose membranes of different porosity and averaged pore size were used as a model of thin porous layers, glass and metal filters were used as a model of thick porous substrates. It has been shown, that the spreading process follows the power law in time in the case of spreading of silicon oil drops over porous substrate saturated with the same oil. The liquid flow in the spreading drop has been matched with the flow in the porous substrate. Both the exponent and the pre-exponential factor of the power law have been predicted and compared with our experimental data, which shows the good agreement. An effective lubrication coefficient has been introduced, which accounts for an effective slippage of liquids over porous substrates. This coefficient has been both theoretically predicted and experimentally verified.
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Kemiha, Mohammed Li Huai Zhi. "Étude expérimentale des écoulements polyphasiques phénomènes interfaciaux /." Vandoeuvre-les-Nancy : INPL, 2006. http://www.scd.inpl-nancy.fr/theses/2006_KEMIHA_M.pdf.
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Lacassagne, Tom. "Oscillating grid turbulence and its influence on gas liquid mass transfer and mixing in non-Newtonian media." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI103/document.
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L’étude du transfert de masse turbulent aux interfaces gaz-liquide est d’un grand intérêt dans de nombreuses applications environnementales et industrielles. Bien que ce problème soit étudié depuis de nombreuses années, sa compréhension n’est pas encore suffisante pour la création de modèles de transfert de masse réalistes (de type RANS ou LES sous maille), en particulier en présence d’une phase liquide à rhéologie complexe. Ce travail expérimental a pour but l’étude des aspects fondamentaux du transfert de masse turbulent à une interface plane horizontale entre du dioxyde de carbone gazeux et une phase liquide newtonienne ou non, agitée par une turbulence homogène quasi isotrope. Les milieux liquides non newtoniens étudiés sont des solutions aqueuses d’un polymère dilué à des concentrations variables et aux propriétés viscoélastiques et rhéofluidifiantes. Deux méthodes de mesure optiques permettant l’obtention du champ de vitesse de la phase liquide (SPIV) et de concentration du gaz dissout (I-PLIF) sont couplées tout en maintenant une haute résolution spatiale, afin de déduire les statistiques de vitesse et de concentration couplées dans les premiers millimètres sous la surface. Une nouvelle version de I-PLIF est développée pour les mesures en proche surface. Elle peut également s’appliquer dans différentes études de transfert de masse. La turbulence de fond est générée par un dispositif de grille oscillante. Les mécanismes de production et les caractéristiques de la turbulence sont étudiés. L’importance de la composante oscillante de la turbulence est discutée, et un phénomène d’amplification de l’écoulement moyen est mis en évidence. Les mécanismes du transfert de masse turbulent à l’interface sont finalement observés pour l’eau et une solution de polymère dilué à faible concentration. L’analyse conditionnelle des flux de masse turbulent permet de mettre en évidence les évènements contribuant au transfert de masse et de discuter de leur impact relatif sur le transfert totalThe study of turbulence induced mass transfer at the interface between a gas and a liquid is of great interest in many environmental phenomena and industrial processes. Even though this issue has already been studied for several decades, its understanding is still not good enough to create realistic models (RANS or sub-grid LES), especially when considering a liquid phase with a complex rheology. This experimental work aims at studying fundamental aspects of turbulent mass transfer at a flat interface between carbon dioxide and a Newtonian or non-Newtonian liquid, stirred by homogeneous and quasi isotropic turbulence. Non-Newtonian fluids studied are aqueous solutions of a model polymer, Xanthan gum (XG), at various concentrations, showing viscoelastic and shear-thinning properties. Optical techniques for the acquisition of the liquid phase velocity field (Stereoscopic Particle Image Velocimetry, SPIV) and dissolved gas concentration field (Inhibited Planar Laser Induced Fluorescence, I-PLIF) are for the first time coupled, keeping a high spatial resolution, to access velocity and concentration statistics in the first few millimetres under the interface. A new version of I-PLIF is developed. It is designed to be more efficient for near surface measurements, but its use can be generalized to other single or multiphase mass transfer situations. Bottom shear turbulence in the liquid phase is generated by an oscillating grid apparatus. The mechanisms of turbulence production and the characteristics of oscillating grid turbulence (OGT) are studied. The importance of the oscillatory component of turbulence is discussed. A mean flow enhancement effect upon polymer addition is evidenced. The mechanisms of turbulent mass transfer at a flat interface are finally observed in water and low concentration polymer solutions. A conditional analysis of turbulent mass fluxes allows to distinguish the type of events contributing to mass transfer and discuss their respective impact in water and polymer solutions
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Mathieu, Daniel. "Etude de la dynamique d'étalement de fluides newtoniens et non newtoniens lors d'un processus d'enduction par rotation." Mulhouse, 1997. http://www.theses.fr/1997MULH0468.
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Ce travail porte sur l'étude de l'influence de la rhéologie et des conditions de mouillage sur l'étalement forcé de fluides et sur les instabilités qui en résultent (formation de doigts au voisinage de la ligne de contact). Un dispositif expérimental a été construit permettant l'analyse de la forme d'une goutte en rotation sur une surface horizontale. Différentes techniques optiques ont été mises en oeuvre : photographie, interférométrie et moiré. Le choix des fluides (mélanges et solutions de polydiméthylsiloxane (PDMS) et une huile de polybutène) et des supports solides (plaquettes de silicium) a été particulièrement crucial. L'étalement spontané est conforme à la théorie (peu d'influence de la nature du fluide). Lors de l'étalement forcé des PDMS, la vitesse de variation de l'épaisseur suit parfaitement la loi théorique. Par contre, pour le rayon des gouttes, des différences apparaissent. Elles sont reliées aux différences constatées pour les temps critiques d'apparition des doigts que nous avons définis. Eux-mêmes sont reliés à la présence de macromolécules de masse élevée en solution. L'influence de la rhéologie du fluide sur les instabilités est ainsi mis en évidence. L'analyse spectrale du contour de la goutte nous indique le mode dominant de l'instabilité et sa cinétique de croissance. Ils dépendent des conditions de mouillage. Ainsi la forme, le nombre et la croissance des doigts sont très différents en mouillage partiel. Comme la forme du bourrelet semble relié à l'instabilité, nous avons donc tenté de reconstruire le profil de la goutte à partir du moiré. Des résultats prometteurs mais partiels ont été obtenus. Enfin, les expériences de relaxation nous ont permis d'étudier les lois de démouillage de films métastables.
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Cordonnier, Benoit. "Non-Newtonian effects in silicate liquids and crystal bearing melts." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-106475.
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THOMPSON, RONEY LEON. "PERFORMANCE OF A NEW CONSTITUTIVE EQUATION FOR NON NEWTONIAN LIQUIDS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=18975@1.
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Materiais não Newtonianos reagem de maneira diferente quando expostos a esforços cisalhantes ou extensionais. Uma equação constitutiva em que a tensão é função não só da taxa de deformação, mas também do tipo de escoamento é proposta e analisada teoricamente. Ela combina as informações obtidas em cisalhamento, extensão e movimento de corpo rígido em todas as regiões de um escoamento complexo. Esta equação é testada em códigos numéricos para duas geométricas axissimétricas diferentes: a contração abrupta 4:1 e o canal convergente R (2) z = C. Ambas as geometrias têm sido usadas para efetuar medições da viscosidade extensional. Para validação do modelo, foi construída uma seção de testes com uma contração abrupta 4:1. Foram feitos experimentos com fluidos Newtonianos e viscoelásticos utilizando a técnica de Velocimetria por Imagens de Partículas para determinação do campo de velocidade.Non-Newtonian materials exhibit different behavior if submitted to shear or extension. A constitutive equation in wich the stress is a function not only of the rate of deformation, but also of the type of the flow is proposed and analyzed theorecticaly. It combines information obtained in shear, extension and rigid body motion in all regions of a complex flow. This equation is tested with numerical codes for two different axissymmetrical geometries, namely, the 4:1 abrupt contraction and the R(2)z=C convergent channel. Both geometries have been employed to measure the extensional viscosity. In order to validate the model, a test section was buit with a 4:1 contraction. Newtonian and viscoelastic fluids were tested using the Particle Image Velocimetry technique to determine the velocity field.
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VARGES, PRISCILLA RIBEIRO. "LIQUID-LIQUID DISPLACEMENT FLOWS IN A HELE-SHAW CELL INCLUDING NON-NEWTONIAN EFFECTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=16992@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEstudou-se neste trabalho o deslocamento de fluidos em meios porosos utilizando células de Hele-Shaw. Especificamente, investigou-se experimentalmente o deslocamento de um fluido não newtoniano por um newtoniano em uma célula retangular de Hele-Shaw. A instabilidade de Saffman-Taylor ou viscous fingering é um fenômeno observado quando um fluido de menor viscosidade desloca um de maior viscosidade, e a célula de Hele-Shaw é uma ferramenta conveniente para a sua observação. Esse fenômeno é muito importante em diversas aplicações, como por exemplo: recuperação secundária e terciária de petróleo, invasão de fluidos de perfuração em meios porosos, fraturamento hidráulico, processamento de polímeros, hidrologia e filtração. É vasta a literatura relativa ao estudo de fluidos newtonianos e não newtonianos deslocados por ar em células de Hele-Shaw. Entretanto, existem poucos trabalhos envolvendo deslocamentos de líquidos com viscosidades comparáveis, ou seja, razão de viscosidade diferente de zero. Apresentou-se o detalhamento do projeto de construção de uma célula de Hele-Shaw aplicável ao deslocamento de um líquido por outro líquido. A evolução da forma da interface foi analisada, através de uma câmera fotográfica, em função dos parâmetros geométricos, dinâmicos e reológicos. A partir da vetorização da forma da interface, determinou-se a eficiência do deslocamento. Sendo assim, foi definido o espectro de situações em que há formação de fingers e plugs relativos ao deslocamento de goma xantana por um óleo mineral. Não há na literatura uma convenção universal para apresentação dos resultados, logo uma contribuição original refere-se à adimensionalização proposta onde os principais parâmetros governantes são a velocidade adimensional, o número de capilaridade reológico e o índice de comportamento da goma xantana. Observou-se que para um valor constante do índice de comportamento e para um valor do número de capilaridade reológico da ordem de 10-1, a eficiência de deslocamento aumenta com a velocidade adimensional, porque a razão de viscosidade diminui.
This work studied the displacement of fluids in porous media using a Hele-Shaw cell. Specifically, was investigated experimentally the displacement of a non-Newtonian fluid by a Newtonian in a rectangular Hele-Shaw cell. The Saffman-Taylor or viscous fingering instability occurs when one fluid pushes a more viscous one, and a Hele-Shaw is a convenient tool to the phenomenon observation. Applications include displacement of heavy crude oil in reservoirs, drilling fluid invasion through porous media, fracture conductivity, polymer processing, hydrology and filtration. The Saffman-Taylor instability has been extensively studied for Newtonian and non-Newtonian liquids displaced by air in a Hele-Shaw cell. However displacement flows involving two liquids of comparable viscosity (nonzero viscosity ratio) have received very little attention. It was presented the details of construction of a Hele-Shaw applicable to a liquid-liquid displacement. The evolution of the shape of the interface was analyzed through a digital camera, as a function of the geometric, dynamic and rheological parameters. From tracing the shape of the interface, was determined the displacement efficiency. Thus, it was defined the spectrum of situations in which there is formation of fingers and plugs relating to displacement of xanthan gum by a mineral oil. There is no universal convention in the literature for presenting the results so a original contribution concerns the proposed dimensionless parameters. The main parameters that govern this flow are the dimensionless flow rate, the rheological capillary number and the behavior index of xanthan gum. It was observed that for a constant value of the behavior index and for a rheological capillary number of magnitude of 10-1, the displacement efficiency increases with the dimensionless flow rate, because the viscosity ratio decreases.
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AZEVEDO, PATRICIA EMIDIO DE. "LIQUID-LIQUID DISPLACEMENT FLOWS IN A HELE-SHAW CELL INCLUDING NON-NEWTONIAN EFFECTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26868@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
A perfuração de poços de petróleo, principalmente em ambientes offshore, é uma operação que demanda um custo muito elevado, portanto a minimização de problemas e danos ao reservatório produtor é muito importante. O projeto de um fluido de perfuração que garanta a mínima invasão na rocha reservatório é um tópico fundamental, como consequência a indústria petrolífera tem investido em estudos com o intuito de evitar que este problema ocorra. Sendo assim, nesse trabalho estudou-se o escoamento de fluidos em um meio poroso ideal, a célula de Hele-Shaw. Para realizar esse trabalho foram utilizados dois fluidos não newtonianos: uma solução aquosa de um polímero flexível, a poliacrilamida; e uma solução aquosa de um polímero rígido, a goma xantana. Esses fluidos não newtonianos representaram o fluido de perfuração, já o papel do petróleo presente na rocha reservatório foi desempenhado pelo óleo mineral. A partir desse experimento é possível observar a instabilidade de Saffman-Taylor ou viscous fingers, que é um fenômeno observado quando um fluido de menor viscosidade desloca outro de maior viscosidade. Esse fenômeno é muito importante em diversas aplicações, tais como: invasão de fluido de perfuração em meios porosos (caso que será estudado), recuperação secundária e terciária de petróleo, fraturamento hidráulico, processamento de polímeros, hidrologia e filtração. O experimento consiste em analisar a evolução da interface entre os dois fluidos através de uma câmera filmadora. A partir das imagens é determinada qualitativamente a eficiência do deslocamento. Com o conjunto de imagens é possível observar também em quais parâmetros dinâmicos e reológicos ocorre a transição fingers (interface instável) para plug (interface estável), e viceversa. Também foram realizados testes reológicos nos quais foi possível conhecer o comportamento dos fluidos não newtonianos utilizados. Com base nos dados coletados observou-se que tanto para a poliacrilamida quanto para a goma xantana a transição ocorre a uma taxa de cisalhamento adimensional próxima de 3.
The drilling of oil wells, particularly in offshore environments, is an operation which demands a high cost, thus, the minimization of problems and damage to the producing reservoir is very important. The design of a drilling fluid that ensures minimum invasion into the reservoir rock is a major topic, consequently the oil industry has invested in research in order to prevent this problem from occurring. Therefore, this research studied the displacement of fluids in an ideal porous medium, a Hele-Shaw cell. To accomplish this task, the following two non-Newtonian fluids were used: an aqueous solution of a flexible polymer, polyacrylamide; and the other an aqueous solution of a rigid polymer, xanthan gum. Such non-Newtonian fluids represent the drilling fluid, while the function of oil present in the reservoir rock was represented by mineral oil. From this experiment it is possible to observe the Saffman-Taylor instability or viscous fingers, which is a phenomenon observed when a low viscosity fluid displaces a higher viscosity fluid. This phenomenon is very important in many applications, such as drilling fluid invasion in porous media, secondary and tertiary oil recovery, hydraulic fracturing, polymer processing, hydrology and filtration. The experiment consists in analyzing the evolution of the interface between two fluids through a digital camera, and determining the displacement efficiency qualitatively from the imagens. With the set of images is possible to observe in which dynamic and rheological parameters the transition from fingers (unstable interface) to plug (stable interface) occurs, and vice versa. Also, rheological tests were performed in which it was possible to know the behavior of non-Newtonian fluids used in the study. From the data collected it was observed that both the polyacrylamide and for xanthan gum transition occurs near the dimensionless shear rate of 3.
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Gilbert, Christopher Donald. "Non-newtonian conversion of type II emulsion liquid membranes-solving long-standing permeability, stability, and swelling problems." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/11746.
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Goshawk, Jeffrey Alan. "Enhancement of the drainage of non-Newtonian liquid films by oscillation." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333685.
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Yim, Samson Sau Shun. "The effect of flow stability on residence time distribution of Newtonian and non-Newtonian liquids in couette flow." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264191.
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Kheng, Tan Ka. "Gas diffusion into viscous and non-Newtonian liquids and the onset of convection." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321528.
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Arnaud, René. "Hydrodynamique et transfert thermique dans les milieux gaz-liquides non newtoniens agités mécaniquement." Aix-Marseille 3, 1990. http://www.theses.fr/1990AIX30073.
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L'etude prealable de l'hydrodynamique, dans les milieux non newtoniens (pseudoplastiques) agites et aeres, vient supporter celle du transfert thermique a partir d'un serpentin immerge, en discernant trois zones: engagement-desengagement-dispersion; et un point de fonctionnement particulier: le point de desengagement complet. La confrontation des resultats avec ceux obtenues dans les milieux non aeres et/ou newtoniens, nous renseigne sur leurs differences de comportement. Si les correlations hydrodynamiques newtoniennes peuvent etre etendues aux fluides pseudoplastiques, celles decrivant le transfert thermique apparaissent specifiques. Il existe, pour les milieux pseudoplastiques moderes, un diametre de mobile d'agitation limite, au-dessus duquel se manifeste un effet de mur prejudiciable au transfert thermique (cet effet est inexistant en milieu aere). La puissance d'agitation semble le meilleur critere d'extrapolation. Si une extrapolation a partir du flux thermique est necessaire, la similitude geometrique peut etre conservee sous certaines conditions. La prise en compte de l'incidence de l'aeration sur le gradient de vitesse, a proximite du serpentin, devient necessaire au-dessus d'une valeur limite du desengagement complet thermique. Ces etudes ont ete menees en respectant une methodologie experimentale precise (analyse de donnees, plans d'experiences, calcul d'erreur. . . ), et proposent des correlations dont les qualites sont appreciees par un systeme de mutation statistique original
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Crumeyrolle, Olivier. "Étude expérimentale des liquides viscoélastiques dans le système de Couette-Taylor." Le Havre, 2002. http://www.theses.fr/2002LEHA0014.
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Nous avons étudié expérimentalement l'influence de la viscoélasticité de solutions aqueuses de polyoxyéthylène (POE) de grande masse molaire sur l'écoulement de Couette-Taylor à cylindre extérieur fixe. Avec les solutions les moins viscoélastiques, les deux premiers modes d'instabilités observés sont semblables au cas newtonien : rouleaux de Taylor, rouleaux ondulés. Pour le POE le moins polydisperse, un net comportement de stabilisation puis de déstabilisation a été observé quand la concentration augmente, en accord qualitatif avec la théorie. Si la concentration est suffisante, l'amplitude des oscillations des rouleaux ondulés diminue au-delà du seuil, à l'inverse du cas newtonien. Pour les solutions les plus viscoélastiques, qui sont rhéofluidifiantes, le premier mode d'instabilité est oscillant. Il est constitué de deux ondes contrapropagatives fortement couplées. Au-delà du seuil, il y a apparition de défauts qui conduisent à des motifs désordonnés, tandis que le couplage diminueExperimental investigation of the stability of viscoelastic Couette-Taylor flow with fixed outer cylinder was conducted for aqueous solutions of high molecular weight polyethyleneoxide (PEO). For solutions with low viscoelasticity, the first and second instability odes are similar to the Newtonian case: Taylor Vortex Flow, Wavy Vortex Flow. For the lowest polydispersity PEO, a clear stabilisation behavior was observed, followed by destabilisation when concentration was increased, in qualitative agreement with theory. For ufficient concentrations, spatial amplitude of WVF decreased above onset, contrary to the Newtonian case. For solutions with higher viscoelasticity, which was concomitant with higher shear-thining, the first instability mode appeared to be oscillatory, in form of two strongly coupled counterpropagating waves. Above onset, some defects appeared and drove the flow to a disordered state while coupling decreased
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Cordonnier, Benoît. "Non-Newtonian effects in silicate liquids and crystal bearing melts : implication for magma dynamics." kostenfrei, 2009. http://edoc.ub.uni-muenchen.de/10647/.
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Ciceron, Delphine. "Etude de la fluidisation de particules de formes diverses par des liquides non-newtoniens." Nantes, 2000. http://www.theses.fr/2000NANT2113.
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L'objectif principal de ce travail est la caracterisation du minimum de fluidisation et de l'expansion de particules spheriques avec ou sans distribution de taille et de particules non spheriques fluidisees par des liquides non newtoniens purement visqueux. Nous avons tout d'abord teste a partir de nombreuses donnees experimentales un modele base sur une representation capillaire des milieux poreux et compare ses predictions a celles des modeles de la litterature. Celui-ci permet une determination satisfaisante de la vitesse au minimum de fluidisation u m f ainsi qu'une bonne caracterisation de l'expansion jusqu'a une porosite limite. Celle-ci depend du type de particules utilise : elle est de 0,65 pour les spheres, 0,80 pour les particules parallelepipediques et 0,85 pour les graviers. Seul le modele capillaire permet une caracterisation correcte de l'expansion des particules fortement anisotropes par rapport aux equations de la litterature. Deux relations empiriques ont ete egalement proposees permettant une evaluation a priori de u m f dans le cas des spheres ne necessitant pas la connaissance de la porosite. Nous avons dans un deuxieme temps developpe un nouveau modele base sur le concept d'objet immerge afin de caracteriser l'expansion des spheres. On a montre qu'il donne des resultats satisfaisants pour des porosites superieures a 0,60. L'association des deux modeles permet de representer la fluidisation du minimum de fluidisation jusqu'aux fortes porosites avec un ecart moyen modele - experience inferieur a 20%. Ce travail a ete etendu a l'etude de l'ecoulement de liquides non newtoniens a travers des lits fixes et fluidises de melange de spheres de tailles differentes. En modifiant le modele capillaire pour tenir
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Kemiha, Mohammed. "Étude expérimentale des écoulements polyphasiques : phénomènes interfaciaux." Vandoeuvre-les-Nancy, INPL, 2006. http://docnum.univ-lorraine.fr/public/INPL/2006_KEMIHA_M.pdf.
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Ce travail est consacré à l'étude expérimentale des écoulements diphasiques et triphasiques d'inclusions en milieux tant newtoniens que non newtoniens à l'échelle microscopique et mésoscopique, en utilisant la vélocimétrie par images des particules (PIV) et la visualisation par une caméra rapide. En milieu viscoélastique et rhéofluidifiant, nous avons caractérisé l'écoulement autour d'une inclusion isolée (gazeuse ou solide) par l'obtention de champs de vitesses. Ces résultats ont permis de confirmer l'origine viscoélastique du sillage négatif et de prédire ses caractéristiques. De nouveaux scénarios de coalescence entre deux bulles dans un train ont aussi été mis en évidence. La traversée d'une interface liquide–liquide par une inclusion a été abordée par des expériences originales, permettant de décrire la dynamique du phénomène et de définir ses nombres adimensionnels dans le cas d'une bulle, et de mettre en évidence des instabilités interfaciales dans le sillage d'une inclusion solide. Enfin, des bulles toriques dans l'eau ont été étudiées expérimentalement de la formation, l'ascension jusqu'à la fragmentationThe present work was devoted to the experimental study of the multiphase flow around inclusions in both Newtonian and non-Newtonian media at respectively microscopic and mesoscopic scales, by means of the particle image velocimetry (PIV) and fast camera visualization. In viscoelastic and shear-thinning fluids, we characterized the flow around an isolated inclusion (gas or solid) by performing the measurements of velocity fields. These results were used to confirm the viscoelastic origin of the negative wake and to describe its characteristics. New coalescence scenarios between two bubbles in a bubble train were also highlighted. The deformation of a liquid-liquid interface due to the passage of an inclusion was investigated by original experiments. The results thus obtained permitted to describe the dynamics of the phenomenon and to define its dimensionless numbers in the case of a bubble, and to put into evidence interfacial instabilities in the wake of a solid inclusion. Lastly, the ring bubbles in water were studied experimentally from the formation, the rise until their fragmentation
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Gilbert, Christopher Donald. "Non-Newtonian conversion of emulsion liquid membranes in the extraction of lead and zinc from simulated wastewater." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/10911.
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De, la Lande Marie-Emmanuelle. "Sur une méthode de simulation numérique d'écoulements de liquides incompressibles, newtoniens et non-newtoniens, basée sur le concept de tubes de courant." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37597069q.
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GUIHARD-JAFFREDO, LAURENCE. "Etude du melangeage circonferentiel et du melangeage axial dans les reacteurs de couette-taylor et de couette-taylor-poiseuille (cas de liquides newtoniens et de liquides non-newtoniens)." Rennes 1, 1989. http://www.theses.fr/1989REN10009.
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Vergne, François. "Le contact élastohydrodynamique ponctuel lubrifié par un fluide visqueux linéaire ou non." Lyon 1, 1989. http://www.theses.fr/1989LYO19005.
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Ce travail est consacre au calcul simultane des champs d'epaisseur, de pression et de contraintes de cisaillement dans un contact elastohydrodynamique (ehd) ponctuel, lisse, lubrifie par un fluide visqueux lineaire ou non lineaire, en regime permanent et isotherme. Le contact ehd lubrifie par un fluide newtonien piezovisqueux est etudie dans la premiere partie. Le comportement newtonien conduit a une determination satisfaisante des epaisseurs de film mais a des forces de frottement de glissement considerablement surestimees. Le contact ehd lubrifie par un fluide de ree-eyring est etudie dans la deuxieme partie. Le probleme de contact est formule en parametres sans dimension. Le glissement et la contrainte caracterisant la non-linearite ont peu d'effet sur les epaisseurs de film. La non-linearite diminue considerablement les contraintes de cisaillement et les forces de frottement qui deviennent realistes. Une methode de resolution globale et plus coherente du probleme de contact ehd est ainsi proposee. Des applications sont presentees dans la troisieme partie. Une bonne concordance est obtenue entre les resultats theoriques et experimentaux tant pour les epaisseurs de film que pour les forces de frottement
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Blašková, Daniela. "Reologické vlastnosti chladicích kapalin pro obrábění kovů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2019. http://www.nusl.cz/ntk/nusl-408017.
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The flow properties of two types of operating and clean coolants (A and B) were measured, both used in metalworking. Four samples of both operating liquids were sampled from the process monthly (from the beginning to the end of its use). All liquids were measured at 25 °C with an oil emulsion content of 4%. In addition, flow curves of pure cooling emulsions with concentration of coolant 2, 4, 6 and 8% were measured at 30, 35, 40, 45 and 50 °C. Rheological measurement was performed at geometry of concentric cylinders. Microbial activity and content of additives (Thermogravimetry) was determined in operating liquid A. Both operating liquids exhibited non-Newtonian behavior. Viscosity increased with the shear rate (10–100 s-1) and impurity level. Although the amount of impurity was approximately the same in both liquids, viscosity varied. For pure liquids, the viscosity increased with increasing concentration and decreased with increasing temperature, except for liquid A with concentration of coolants 6 and 8%, which, depending on the temperature, exhibited both shear thinning, shear thickening and Newtonian behavior. The results shown that impurity level of operating liquids has only minor effect on viscosity and flow properties, but it had an effect on cooling effect. Impurities diluted operating liquids, partial decomposition of the oil component may occur, but in particular, microbial activity causes skin problems of staff. Recommended is to introduce a specific control test for the presence of bacteria.
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Hasan, Duma. "Étude de mélanges fluides solide/liquide concentrés à base de charbon." Compiègne, 1991. http://www.theses.fr/1991COMPA002.
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Le problème posé par la valorisation du charbon micronisé sous forme de fluide aisément manipulable est complexe : il faut élaborer une suspension avec la plus grande concentration massique en combustible et une viscosité d'écoulement la plus faible possible. De plus, le combustible ainsi élaboré doit répondre, lors de la combustion, aux normes de pollution de plus en plus sévères. Le combustible étudié se présente sous forme d'une suspension ternaire charbon décendré d'eau et de fuel appelée : ultracarbofluide (UCF). L'élaboration de ce combustible «nouveau» nécessite une caractérisation complète, notamment en combustion. Ainsi, après une caractérisation rhéologique des mélanges, qui a permis de fixer les teneurs maximales en solide dans les mélanges, une étude de combustion est effectuée. Cette étude de combustion est d'abord réalisée sur le foyer de 100 kW de l'Université de Technologie de Compiègne, sur lequel une sonde de prélèvement isocinétique des particules dans les fumées est mise au point, afin de quantifier les rejets émis lors de la combustion. Enfin, des essais de combustion de l'ultracarbofluide sont effectués en site réel de chauffe, sur une chaudière de 1 MW fonctionnant originellement au fuel, puis reconvertie à un fonctionnement à l'ultracarbofluide.
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Zhu, Chengxiang [Verfasser]. "Numerical Investigation on the Instability and the Primary Breakup of Inelastic Non-Newtonian Liquid Jets / Chengxiang Zhu." München : Verlag Dr. Hut, 2014. http://d-nb.info/1058285599/34.
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Ravi, Vishaul. "Effects of Interfacial and Viscous Properties of Pure Liquids and Polymeric Solutions on Drop Spread Dynamics." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1331300235.
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François, Joseph-Marc. "Modélisation d'écoulements en film mince de fluides newtoniens généralisés : application à la prédiction des caractéristiques de fonctionnement de mécanismes lubrifiés." Lyon 1, 1987. http://www.theses.fr/1987LYO10076.
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Sarma, Sreedhara. "Fluid Mechanics of High Speed Deformable Roll coating. An experimental and theoretical study of film thickness and stability in high speed deformable roll coating flow with Newtonian and non-Newtonian liquids." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14842.
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Bénito, Sylvain. "Modélisation et simulation du comportement mécanique des milieux plastiques mous : mousses liquides, émulsions." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13858/document.
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Ce travail traite de la modélisation du comportement mécanique de matériaux mous, tels que les mousses liquides et les émulsions. La description de la réponse mécanique de tels milieux nécessite la prise en compte de caractéristiques complexes: élasticité aux grandes déformations, écoulement plastique se produisant au delà d'un certain seuil de contrainte. Nous proposons un nouveau modèle mécanique incluant ces caractéristiques. Une analyse mathématique du couplage entre l'équation constitutive obtenue et l'hydrodynamique est proposée. Le travail s'achève avec une étude numérique du système dans un contexte d'écoulement bidimensionnel. Les simulations reproduisent certains phénomènes observés expérimentalement, tel que la formation de bandes de cisaillementAbstract
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Hassan, Raouf. "Etude expérimentale et modélisation du transfert de matière gaz-liquide en cuve agitée en présence de fluides non-Newtoniens simulant des boues de station d'épuration." Nantes, 2011. http://www.theses.fr/2011NANT2037.
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S'inscrivant dans le contexte de la digestion aérobie thermophile autotherme (ATAD) des boues, cette thèse est dédiée à l'étude de l'effet des propriétés rhéofluidifiantes de la phase liquide sur le transfert de matière gaz-liquide dans un digesteur de laboratoire (cuve agitée aérée en volume). Les boues étant un milieu complexe, il a été initialement choisi d'utiliser des fluides modèles (CMC, gomme de xanthane) dont les formulations sont déduites de la rhéologie des boues. Un jeu de 150 mesures de coefficients volumiques de transfert de matière gaz-liquide est établi, préalablement validé par la mise en œuvre de méthodes physique et chimique et la quantification de la contribution de l'aération de surface. A partir de là, une analyse dimensionnelle rigoureuse est développée afin de modéliser les variations de kLa lorsque la viscosité est dépendante du cisaillement (théorie de la similitude étendue au cas de propriétés variables). Une corrélation sans dimension a pu être établie en décrivant correctement toutes les propriétés rhéologiques (modèle de Williamson-Cross à la place de celui d'Ostwald-de-Waele). En parralèle, des mesures locales de rétention gazeuse et de taille de bulles sont réalisées (double sonde optique). Elles apportent des éléments de compréhension sur la manière dont la rhéologie de la phase liquide affecte transfert de matière gaz-liquide. Enfin, des simulations numériques d'écoulements sont réalisées dans ce réacteur de laboratoire et servent d'outil complémentaire pour étudier le transfert de matière gaz-liquide dans de tels milieuxIn keeping with the context of sludge Autothermal Thermophilic Aerobic Digestion, this thesis reports investigations on the effects of shear-thinning properties of liquid phase on gas-liquid mass transfer inside a labscale ATAD reactor (volume-aerated stirred vessel). Sludge being a complex material, it has been chosen as a first step to use model fluids (CMC, xanthan gum) which formulation is deduced from sludge rheological characteristics. A set of 150 measurements of overall volumetric gas-liquid mass transfer coefficients is carried out. For validation purposes, both physical and chemical methods are tested and the relative contribution between surface and volume aerations is quantified. Supported by this database, a consistent dimensional analysis is proposed so as to rigorously model the variations of kLa when viscosity is dependent on shear rates (extension of the theory of similarity to the case of variable material properties). A unique dimensionless correlation is then obtained, provided that all the rheological properties are correctly taken into account (Williamson-Cross's model instead of Ostwald-de-Waele's model). In parallel, some local measurements of gas hold-up and bubble size are performed by means of a double-tip optic probe. They give some interesting elements for better understanding how and why the liquid rheology affects the absorption rates. At last, some numerical investigations inside this lab-scale ATAD reactor are presented and used as a complementary tool for studying the effect of rheology on gas-liquid hydrodynamics and mass transfer
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Arjmandi-Tash, Omid. "Interaction of droplets and foams with solid/porous substrates." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/24889.
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Current problems on the interaction of complex liquids (i.e. droplets or foams) with complex surfaces (i.e. soft deformable or porous surfaces) are addressed in the following areas: (1) wetting of deformable substrates and surface forces, (2) kinetics of wetting and spreading of non-Newtonian liquids over porous substrates, (3) kinetics of spreading of non-Newtonian solutions over hair, (4) free drainage of foams produced from non-Newtonian solutions, and (5) foam drainage placed on porous substrates. Equilibrium of liquid droplets on deformable substrates was investigated and the effect of disjoining pressure action in the vicinity of the apparent three phase contact line was taken into account. It was proven that the deformation of soft solids is determined by the action of surface forces inside the transition zone. Spreading/imbibition of blood, which is a power law shear thinning non-Newtonian liquid, over a dry porous layer was investigated from both theoretical and experimental points of view. It was found that blood droplet spreading/imbibition over porous substrates shows two different behaviours: (i) partial wetting case with three subsequent stages: initial fast spreading, constant maximum droplet base and the shrinkage of the droplet base; (ii) complete wetting case with only two stages: initial fast spreading and the shrinkage of the droplet base. The wetting of hair tresses by aqueous solutions of two commercially available polymers, AculynTM 22 (A22) and AculynTM 33 (A33) was investigated experimentally. Both A22 and A33 solutions demonstrate well pronounced shear thinning behaviour. Initial contact angle of the A22 and A33 solutions on hair tresses was about 100o. The A22 droplets remained on the hair tress after spreading for at least half an hour. However, a fast penetration of the A33 droplets inside the hair tresses was observed when advancing contact angle in the course of spreading reached a critical value of about 60o. This could be explained by Cassie-Wenzel wetting transition which is caused by filling the pores inside the porous media by liquid. The influence of non-Newtonian rheology of A22 and A33 solutions on foam drainage was also investigated experimentally and a new theory of foam drainage was presented for the case of free drainage. For lowly viscous polymeric solutions and under the assumption of rigid surface of the Plateau border, the predicted values of the time evolution of the foam height and liquid content were in good agreement with the experimental data. However, in the case of highly viscous solutions an interfacial mobility at the surface of the Plateau border has to be taken into account. A completely new theory of foam drainage placed on porous substrate was developed. It was found that there are three different regimes of the process: (i) a rapid imbibition, the imbibition into the porous substrate dominates as compared with the foam drainage; (ii) an intermediate imbibition, that is, the imbibition into the porous substrate and the rate of drainage are comparable; (iii) a slow imbibition, the rate of drainage inside the foam is higher than the imbibition into the porous substrate for a period of time and a free liquid layer is formed over the porous substrate.
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Park, Yonggyun. "Development and Optimization of Novel Emulsion Liquid Membranes Stabilized by Non-Newtonian Conversion in Taylor-Couette Flow for Extraction of Selected Organic and Metallic Contaminants." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11487.
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Extraction processes employing emulsion liquid membranes (ELMs), water-in-oil emulsions dispersed in aqueous phase, have been shown to be highly efficient in removing a variety of organic and inorganic contaminants from industrial wastewaters. As a result, they have been considered as alternative technologies to other more common separation processes such as pressure-driven membrane processes. Unfortunately, a widespread use of the ELM process has been limited due to the instability of emulsion globules against fluid shear. Breakup of emulsions and subsequent release of the internal receptor phase to the external donor phase would nullify the extraction process. Numerous studies have been, therefore, made in the past to enhance the stability of ELMs. Examples include adding more surfactants into the membrane phase and increasing the membrane viscosity. However, increased stability has been unfortunately accompanied by loss in extraction efficiency and rate in most reported attempts.
The primary objective of this research is to apply the ELMs in a unique contacting device, a Taylor-Couette column, which provides a relatively low and uniform fluid shear that helps maintaining the stability of emulsion without compromising the extraction efficiency of a target compound. The ELM used in this study is made of membrane phase converted into non-Newtonian fluid by polymer addition, which provides additional uncommon remedy for the problem. This innovative ELM process was optimized to treat various types of simulated industrial wastewaters containing selected phenolic compounds and heavy metals. Experiments performed in this study suggested that the newly developed ELM process achieved exceptionally high overall removal efficiencies for the removal of these target compounds in relatively short contact time. Mechanistic predictive models were further developed and verified with the experimental data. Combined with the experimental data and novel mathematical predictive models, this study is expected to have a high impact on immediate practices of emulsion liquid membrane technologies in relevant industries.
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Kamal, Ibrahim Abdelhamid Hossam. "Numerical prediction of a viscoelastic fluid flow past a non-confined cylinder." Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10018/document.
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Ce travail a pour principal objectif la prédiction numérique de l'écoulement laminaire bidimensionnel d'un fluide viscoélastique autour d'un cylindre en milieu non confiné. La méthode des volumes finis en coordonnées orthogonales généralisées est ici adoptée pour résoudre les équations de conservation. Le modèle constitutif pour le fluide est de type Phan-Tien Tanner simplifié (S-PTT). Afin de stabiliser l'algorithme de résolution, le schéma dit "Elastic Viscous Split Stresses" (EVSS) est utilisé. Le code de calcul mis au point a été validé dans le cas de l'écoulement newtonien. Les résultats obtenus corroborent ceux de la littérature. Ensuite, ce code a été appliqué au cas d'un écoulement viscoélastique autour d'un cylindre non confiné. Dans ce cas, l'analyse a été réalisée pour différents nombres de Reynolds (Re = 200) et pour différents nombres de Deborah (0.0~0.25). Aussi, les caractéristiques principales de l'écoulement (les contraintes d'extra tension viscoélastiques, la première différence des contraintes normales et les champs de pression, de vitesses et de rotation) ont été présentées et commentées. Enfin, les évolutions de nombre de Strouhal, de la traînée et de la portance sont montréesThe two-dimensional viscoelasc!ic incompressible fluid flow pas! a non-contined cylinder is numerically simulated. The governing equations are stated in the generalized orthogonal coordinate system. The finite volume method is used to descritize the governing equations. For the viscoelastic constitutive equation. the simplified Phan-Thien-Tanner (SPTT) model is employed. The quadratic scheme QUICK is applied to evaluate the convection terms. The Elastic Viscous Split Stress (EVSS) formulation is used to decompose the stress tensor to enhance the stability of the computations. The developed code is validated for Newtonian and viscoelastic resullts. The present results show good consistency with the published literature. For the Newtonian flow. the obtained results indicate that the onset of the laminar vortex shedding instability occurs at Re >_47. Concerning the viscoelastic fluid. the influences of the Reynolds and Deborah numbers are discussed. The studied flow properties are the extra-shear stress, the first normal stress difference, the pressure field, the flow reeirculation. and the ve!ocity field. Also. the results for the Strouhal number, the drag and the lift are introduced and commented
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Fu, Taotao. "Ecoulements gaz-liquide et comportement des bulles en microcanaux." Thesis, Vandoeuvre-les-Nancy, INPL, 2010. http://www.theses.fr/2010INPL030N/document.
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Les écoulements gaz-liquide constituent un axe de recherche très actif en microfluidique. Le rapport des débits entre les deux phases, la formation de bulles et les champs de vitesse des microcanaux ont été étudiés dans cette thèse, en utilisant une caméra numérique rapide et un microsystème de Particule Image Velocimetry (micro-PIV). En particulier, le diagramme des phases gaz-liquide ont été établi dans des microcanaux carrés ; la formation des bulles en fluides tant newtoniens que non newtoniens a été étudiée en détail dans plusieurs configurations géométriques telles que T-injonction et flow-focusing. Les mécanismes régissant la formation d'une bulle ont été modélisés pour chaque étape : expansion, amincissement et rupture. L'étape amincissement de la traînée d'une bulle est notamment contrôlée par une pression orthogonale qui dépend du débit du liquide. Dans le cadre de flow-focusing, le mécanisme de la rupture du film gazeux peut être décrit par une loi d'échelle reliant l'épaisseur minimale du film au temps restant juste avant la rupture avec un exposant 1/3. Le caractère non newtonien de fluides PAAm allonge la traînée d'une bulle par rapport aux fluides newtoniens. Enfin, l'étude de la coalescence entre bulles a été entreprise à l'échelle microscopique ainsi que le comportement complexe des trains de bulles dans des réseaux de microcannauxGas-liquid two-phase flow is an important research project in microfluidics. The gas-liquid two-phase flow, the bubble formation and moving behaviours in microchannels were investigated, by using a high speed digital camera and a micro Particle Image Velocimetry (micro-PIV). The gas-liquid two-phase flow in vertical rectangular microchannels was investigated and a flow pattern map was constructed; the bubble formation in both Newtonian and non-Newtonian fluids in cross-flowing microfluidic T-junctions and flow-focusing devices was investigated; the bubble formation process could be divided into expansion, collapse and pinch-off stages; the collapse speed of the gaseous thread in the second stage is controlled by the squeezing pressure, and is proportional to the liquid flow rates; while the minimum width of the neck of the gaseous thread in the third stage for bubble formation in flow-focusing devices could be scaled with the remaining time to the ultimate pinch-off as a power law relationship with an exponent of 1/3; the PAAm solutions prolong the gaseous thread in the tangential direction of the neck; bubble coalescence in a microchannel with an expansion section was studied; the bubble behavior in a microchannel with a loop was also investigated
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Dugois, Kévin. "Simulation à l’échelle microscopique et analyse macroscopique de l’imprégnation d’un matériau composite par un fluide chargé en particules." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0011/document.
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Dans le but d’améliorer le comportement thermo-mécanique des aubes de turbine présentes dans les moteurs d’avion développés par SAFRAN, il est nécessaire de mettre au point un nouveau matériau composite. Le procédé de fabrication de ce matériau est complexe et requiert une densification par voie liquide divisée en deux étapes. Cette thèse s’intéresse à la modélisation numérique de la première étape appelée Slurry Cast/APS.Celle-ci consiste en l’injection et le confinement, dans la préforme fibreuse, de particules préalablement mises en suspension. Pour cela, nous avons développé à l’échelle des fibres,un modèle qui utilise les équations de Navier-Stokes incompressibles et monophasiques ,l’équation de Phillips [Phillips et al., 1992] et une loi rhéologique [Krieger, 1972]. Après validation des résultats numériques par comparaison avec des résultats expérimentaux [Hampton et al., 1997] et théoriques [Belfort et al., 1994], le modèle est utilisé pour simuler l’écoulement autour de géométries de tissage proches du matériau étudiéIn order to improve thermo-mechanical behavior of tubine blades in SAFRAN engines plane, a new composite material is necessary. The manufacturing process to obtain this composite is intricate and requires a two steps fluid densification process. This thesis focuses on numerical simulation of the first one called Slurry Cats/APS. In this step, suspended particles are introducted and captured in the reinforcement. For that purpose,we carry out a model at fiber scale, using Navier-Stokes equations in incompressible and monophasic formulation, Phillips equations [Phillips et al., 1992] and a rheological law [Krieger, 1972]. After validation step consisting in a comparison of computational results with experiments [Hampton et al., 1997] and theorical law [Belfort et al., 1994], this model has been used to simulate flow around geometries similar to those encountered in our composite material
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Napitupulu, Farel Hasiholan. "Mesures de la conductivité thermique de fluide non-newtonien à l'aide d'une sonde de mesure de type aiguille, basée sur une méthode thermique impulsionnelle applications aux solutions aqueuses de polymères hydrosolubles et aux suspensions solides/liquides concentrées /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37616961q.
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Mendes, Caroline Eliza. "Avaliação das condições hidrodinâmicas, de transferência de oxigênio e de cisalhamento em diferentes modelos e escalas de reatores pneumáticos." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/7928.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Due to the high capacity of oxygen transfer and versatility, pneumatic reactors have been constantly used in bioprocesses. However, aiming to expand the use of these bioreactors in the industry, as well as increase the understanding of the complex phenomena that occur in these devices, this thesis aimed to evaluate the hydrodynamic, oxygen transfer and shear conditions in three models of pneumatic reactors (bubble column, concentric-tube airlift and split-cylinder airlift) in the scales of 5 and 10 L, using as liquid phase four Newtonian fluids and eight non-Newtonian fluids, and five specific air flow rate (air of 1 to 5 vvm). Related to the hydrodynamic were studied the global gas hold-up (g), the gas hold-ups in the riser (R) and in the downcomer (D), liquid circulation time (tC), superficial liquid velocity in the riser (ULR) and in the downcomer (ULD), and the percentage energy losses in the riser (%ER+%EFR), in the downcomer (%ED+%EFD), and in the bottom (%EB) of airlift reactors. The values of g, R, D, ULR and ULD showed increasing behaviour with increase of air and decreasing behaviour with the kinematic liquid viscosity (L) and the rheologic properties (K e n), and observed the opposite for tC. The higher values of g, R, D and tC were obtained for concentric-tube airlift reactor (ACC) and scale of 10 L. With exception of ULR of Newtonian fluids, the others liquid velocity tests resulted in higher values for split-cylinder airlift reactors (ASC) and scale of 10 L. This result was attributed to the greater driving force (R-D) to liquid circulation obtained in the ASC reactors and the higher energy losses in the riser and in the downcomer observed in the ACC reactors. In the bottom of the airlift reactors, the higher values of %EB were obtained to the ASC reactor. To evaluate the mass transfer were studied, the average bubble diameter (Db), the volumetric oxygen transfer coefficient (kLa) and the terms that compose the kLa, the convective mass transfer coefficient (kL) and the specific interfacial area of mass transfer (aL). With the increase of air, L, K and n, the air bubbles were predominantly coalescent in water, presenting distorted shape, and non-coalescent with spherical/elliptical shape in the other solutions. It was observed a similar behavior between the kLa and aL parameters, which were directly proportional to the air and inversely proportional to the L, K and n. In water, the aL values were lower than glycerol solutions due to the higher Db values observed in this liquid. For the kL, it was observed a decreasing behaviour with the increase of the air in the most solutions. The magnitude of kL values was due mainly the oxygen difusivity in the liquid, and the higher values were observed to the water, following by the non-Newtonian solutions. In general, the higher values of the mass transfer parameters were obtained in the ACC reactor and in the scale of 10 L. The proposed method to the estimate the average shear rate velocity based on Kolmogorov’s theory of isotropic turbulence showed results consistent with the literature relative to the behavior and magnitude of this variable, as well as the results obtained by the analysis of the morphological changes of Streptomyces clavuligerus in two models of airlift reactors and two aeration conditions. Were proposed correlations to predict all evaluated parameters. Were obtained in all cases a good fit with the experimental data, with deviations between the calculated and experimental values below 20%.
Devido à alta capacidade de transferência de oxigênio e versatilidade, reatores pneumáticos têm sido constantemente utilizados em bioprocessos. Entretanto, visando ampliar a utilização destes reatores na indústria, assim como aumentar a compreensão dos fenômenos complexos que ocorrem nestes dispositivos, na presente tese teve-se como objetivo avaliar as condições hidrodinâmicas, de transferência de oxigênio e de cisalhamento em três modelos de reatores pneumáticos (coluna de bolhas, airlift de cilindros concêntricos e airlift split-cylinder) nas escalas de 5 e 10 L, utilizando como fase líquida quatro fluidos newtonianos e oito fluidos nãonewtonianos e cinco vazões específicas de ar (ar de 1 a 5vvm). Em termos hidrodinâmicos foram estudadas as retenções gasosas global (g), no riser (R) e no downcomer (D), tempo de circulação do líquido (tC), velocidade superficial do líquido no riser (ULR) e no downcomer (ULD) e as perdas percentuais de energia no riser, no downcomer e na base (%EB) de reatores airlift. Os valores de g, R, D, ULR e ULD apresentaram comportamento crescente com o aumento de ar e decrescente com a viscosidade cinemática do líquido (L) e propriedades reológicas (K e n), sendo observado o oposto para tC. Os maiores valores de g, R, D e tC foram obtidos em reator airlift de cilindros concêntricos (ACC) e escala de 10 L. Com exceção de ULR de fluidos newtonianos, os demais testes de velocidade do líquido resultaram em maiores valores nos reatores airlift split-cylinder (ASC) e escala de 10 L. Tal resultado foi atribuído a maior força motriz (R-D) para circulação do líquido obtida em ASC e às maiores perdas de energia no riser e no downcomer observadas em reatores ACC. Na base dos reatores, os maiores valores de %EB foram obtidos para reator ASC. Para avaliação da transferência de massa foram estudados o diâmetro da bolha (Db), o coeficiente volumétrico de transferência de oxigênio (kLa) e os termos que o compõe, coeficiente convectivo de transferência de massa (kL) e área interfacial específica de transferência de massa (aL). Bolhas de ar, com o aumento de ar, L, K e n foram predominantemente coalescentes em água, apresentando formato distorcido e nãocoalescentes com formato esférico/elíptico nas demais soluções. Observou-se um comportamento análogo entre kLa e aL, com relação direta à ar e inversa à L, K e n. Em água, os valores de aL foram inferiores às soluções de glicerol em virtude do maior Db observado neste líquido. Para kL, observou-se um comportamento decrescente com o aumento de ar na maioria das soluções. A magnitude dos valores de kL obedeceu principalmente a difusividade do oxigênio no líquido, sendo os maiores valores observados para água, seguido das soluções não-newtonianas. De maneira geral, os maiores valores dos parâmetros de transferência de massa foram obtidos em reator ACC de 10 L. O método proposto para estimativa da taxa de cisalhamento com base na teoria de turbulência isotrópica de Kolmogorov apresentou resultados condizentes com a literatura em termos de comportamento e magnitude desta variável, assim como com os resultados obtidos pela análise das alterações morfológicas de Streptomyces clavuligerus em dois modelos de reatores airlift e duas condições de aeração. Para todos os parâmetros avaliados foram propostas correlações para sua predição, sendo obtidos em todos os casos bons ajustes aos dados experimentais com desvios inferiores à 20%. Palavras-chave: reatores pneumáticos, retenção gasosa, kLa, diâmetro da bolha, velocidade