La compréhension des phénomènes physico-chimiques intervenant dans le processus de déstabilisation des émulsions est fondamentale pour prédire le comportement au jeune âge des mélanges à l’émulsion de bitume. Ce travail de thèse vise à identifier les différents mécanismes et à déterminer les paramètres influant sur la stabilité d’émulsions directes concentrées dans des conditions de non séchage. Afin d’étudier la rupture des émulsions, des systèmes modèles et réels ont été formulés avec différentes huiles (bitume, huiles de silicone et d’hexadécane) et différents tensioactifs cationiques (sel d’ammonium quaternaire et diamine). Pour simuler les phénomènes (relargage d’espèces ioniques en solution avec ou sans remontée de pH) intervenant lors de la mise en contact des émulsions avec les granulats, différentes solutions électrolytiques (NaOH, NaCl et KBr) ont été utilisées pour les déstabiliser. Le comportement des systèmes a été étudié en cours de déstabilisation. Des méthodologies et des outils ont été mis en place et ont permis de classer les émulsions selon leur processus et cinétiques de déstabilisation en réalisant des observations macroscopiques, microscopiques et en utilisant la rhéologie (plus particulièrement l’évolution de l’angle de phase du liant). Ces travaux ont permis d’identifier les mécanismes (floculation, coalescence et percolation) intervenant dans le processus de déstabilisation et de déterminer les paramètres influant tels que la concentration en électrolyte, la température et la composition du bitume. Enfin l’action des fractions cristallisables et des acides naphténiques du bitume sur la déstabilisation des émulsions a été établie et discutée. / Understanding the physical-chemical phenomena occurring in the emulsion breaking process is fundamental to predict the behavior of bitumen emulsion cold mixtures at fresh state. This work aims to identify the different mechanisms involved, and determine the parameters influencing the stability of concentrated oilin- water emulsions without drying. To study the emulsion breaking, models and real systems have been formulated with different oils (bitumen, silicone and hexadecane oils) and different cationic surfactants (quaternary ammonium salt and diamine). In order to simulate the phenomena (release of ionic species in solution with or without pH rising) occurring when the emulsion is put into contact with the aggregates, different electrolyte solutions (NaOH, NaCl and KBr) were used as destabilizing agent. The emulsions behavior was monitored throughout the destabilization using specifically developed methodologies and tools. Emulsions have been ranked in function of their destabilization kinetics and process by performing macroscopic and microscopic observations and by using rheology (especially by following the phase angle evolution of the binder). This work has permitted mechanisms identification (flocculation, coalescence and percolation) involved in the destabilization process and to determine the main factors influencing it such as electrolyte concentration, temperature and bitumen composition. Finally, the impact on the emulsion destabilization of the crystallized fractions and naphthenic acids of bitumen was demonstrated and discussed.

No description available.

A fluid drop in a Hele-Shaw cell moves due to surface tension driven potential flow. Using equations for the pressure and the Green’s function for the Laplace Equation, we can formulate an integral equation that determines the motion of the boundary of the drop. By discretizing the boundary contour and following the motion of boundary nodes, the time evolution of the drop can be determined from initial conditions. Results of a numerical simulation show the movement of a drop relaxing from coalescence and the motion of a drop undergoing electrowetting.

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When two fluid drops come close enough together to touch, surface tension quickly pulls the drops together into one larger drop. This is an example of a singular fluid flow, as the topology of the interface changes at the moment of contact. Similarly, when a pair of bubbles touch, the surface topology changes and a singular flow begins. Since the stress from surface tension depends on the surface curvature, these singularities are often characterised by divergent fluid velocities. Experimental observation or numerical simulation of these flows is therefore difficult due to the high velocities and small lengthscales. In this thesis, I will find multi-scale theoretical solutions for the singular flows during the initial stages of the coalescence of bubbles and drops, solving for the velocity field in the fluid and the rate of coalescence. Each solution has several lengthscales, and on each lengthscale, we must solve some form of the Navier--Stokes equations. I will employ a variety of analytical and numerical techniques to solve for the flow on each scale. These asymptotic solutions are valid at early times; future numerical simulations of the subsequent flow could be initialised with these solutions, rather than the actual singularity. In the course of solving for these singular flows, I will also describe the solution for the motion of a stretched fluid edge, the retraction of a narrow fluid wedge, the capillary flow around a parabola, and the effect of a time-dependent force on a fluid half-space. These fundamental flows have applications outside of coalescence, which I will outline throughout the thesis.

No description available.

Les mousses liquides sont très utilisées dans l'industrie comme dans la vie quotidienne. Cependant, leur stabilité n'est ni complètement comprise ni complètement maîtrisée, la formulation étant essentiellement empirique. Il est donc difficile d'une part de prédire la capacité d'une solution de tensioactifs à générer des mousses et d'autre part de prédire et de contrôler leur déstabilisation. Ce travail de thèse propose des expériences conceptuellement simples qui s'appuient sur le caractère multi-échelle des mousses pour tenter d'établir des liens clairs entre physico-chimie et mécanismes de déstabilisation. Dans un premier temps, nous avons revisité une expérience d'entraînement de films liquides sur un cadre pour illustrer la stabilité des films lors de la génération des mousses ou pendant un réarrangement (processus T1). Nous avons mis en lumière l’existence de deux régimes. Un régime dit non confiné, pour lequel la stabilité des films et réduite et dépend de la physico-chimie. Un régime dit confiné pour lequel le rôle de la physico-chimie est limité et la stabilité est majoritairement contrôlée par l’hydrodynamique.Dans un second temps nous nous sommes intéressés à l'influence de la physico-chimie et de la fraction liquide sur la compétition entre coalescence et mûrissement grâce à l'étude d'une unique couche de bulles (mousse 2D). Nous proposons une méthode de mesure in situ de la perméabilité des films par l'étude simple et rapide du régime transitoire du mûrissement de mousses 2D. Nous avons observé une corrélation entre coefficient de diffusion du gaz contenu dans les bulles et perméabilité.Enfin nous décrivons les résultats d’une expérience spatiale sur le vieillissement à temps long des mousses humides (fraction liquide supérieure à 30% en volume), extrêmement difficile sur Terre à cause du drainage gravitaire, et à laquelle nous avons participé. / Liquid foams are widely used in industry and in everyday life. However, their stability is not fully understood or fully controlled, their formulation being essentially empirical. It is therefore difficult to predict the ability of a surfactant solution to generate foam and to control their destabilization. This thesis proposes simple experiments that rely on the multi-scale nature of foams in order to attempt to establish clear links between physical chemistry and stability.First of all, we revisited an experiment of liquid films entrainment to illustrate the stability of foam films during generation or rearrangement (T1 process). We have shown the existence of two regimes: (i) a unconfined regime, for which the stability of films is reduced and depends on physical chemistry and (ii) a confined regime for which the role of physical chemistry stability is limited and is mainly controlled by hydrodynamics.Secondly, we investigated the influence of physical chemical and liquid fraction on the competition between coalescence and coarsening thanks to the study of a single layer of bubbles (2D foam). We propose a method for in situ measurement of the permeability of films by simple and fast study of the transient regime of coarsening in 2D foam. We observed a correlation between diffusion coefficient of gas and permeability.Finally we describe the results of a space experiment on wet foam aging at large times (volume liquid fraction higher than 30%), extremely difficult on Earth because of gravity drainage, and to which we participated.

A theoretical study of the approach and collision of liquid-drop pairs is performed with results obtained numerically. The collision process is modeled by a squeeze-flow problem involving both planar and non-planar geometry, with attention given to the deformation of the interacting interfaces. Based on the nature of the collision process, an analogy is made between the fluidic systems of colliding liquid bodies and a mechanical mass- spring-damper system. Examination of the analogous mechanical system yields the derivation of an effective damping ratio, ζ*, which is used to predict the outcome of the drop-drop collisions. Predictions made by utilizing the effective damping ratio are then compared to experimental results presented in literature. / text

This dissertation pays critical attention to the "community" concept in archaeological research, casting it as the flexible and impermanent loci of identity formation and social reproduction. In three articles, it investigates various iterations and transformations of the Arikara community in North Dakota after European contact. First, I examine the ethnohistoric record of the Upper Missouri River to investigate how increased flexibility in Arikara settlement strategies during the eighteenth and nineteenth centuries yielded new community configurations, with particular emphasis on Arikara coresidence with their occasional enemies, the Mandans. The second article analyzes archaeological spatial data to elucidate how the organization of open space at the nineteenth- century coalescent settlement of Like-A-Fishhook Village structured interactions between the Arikara and the Mandan-Hidatsa. The third article explores how the Arikara navigated the reconfiguration of their community space as a result of allotment policies during the early twentieth century, and how the now-inundated settlement of Nishu is situated in the social memory and contemporary identity of the Arikara people. The Arikara case demonstrates that social and spatial configurations of community are not always commensurate, and that understanding the multidimensionality of belonging requires both archaeological and ethnographic approaches.

In this thesis we focus on a novel experimental exploration of fluid-driven fractures in a brittle hydrogel matrix. Fluid-driven fracturing is a procedure by which a fracture is initiated and propagates due to pressure applied by a fluid introduced inside the fracture. We describe how to construct the experimental setup utilised in this research, including how to synthesise polyacrylamide hydrogels to study the processes linked with fluid-driven fracturing. These transparent, linearly elastic and brittle gels permit fracturing at low pressures and speeds allowing accurate measurements to be obtained. The broad range of modulus and fracture energy values attainable from this medium allow the exploration of particular regimes of importance. Fracturing within these hydrogels also creates beautiful spiral patterns on the plastically deformed surfaces. We analyse these patterns and discuss their formation, while also commenting on their fractal-like nature. Initially, we study single fractures that are driven by an incompressible Newtonian fluid, injected at a constant rate into an elastic matrix. The injected fluid creates a radial fracture that propagates along a plane. We investigate this type of fracture theoretically and then verify the scaling predictions experimentally. We examine the rate of radial crack growth, fracture aperture, shape of the crack tip and internal fluid flow field. We exhibit the existence of two distinct fracturing regimes, and the transition between these, in which propagation is either dominated by viscous flow within the fracture or the material toughness. Particle image velocimetry measurements also strikingly show that the flow in the fracture can alter from an expected radial symmetry to circulation cells, dependent on the regime of propagation. We then expand our research to the problem of two coplanar fluid-driven radial fractures. This was chosen to focus on the physical mechanisms that are key to fracture network formation, related to many geophysical and industrial practices. Initially, the two fractures propagate independently of each other. At a critical separation they begin to interact, with non-uniform growth occurring along the fracture edges due to the evolving stress state in the gel matrix. When the radial extents of the fractures become sufficiently large, they coalesce and form a bridge between them. Following initial contact, a large increase in flow is seen into the newly created bridge and most of the growth is localised along this, perpendicular to the line connecting the injection sources. From experimental measurements, we observe a universal dynamic behaviour for the growth of this bridge. We model this universal behaviour theoretically and construct scalings related to the growth after coalescence, which again identifies both a viscous and toughness regime. The toughness regime is verified experimentally for the bridge growth and the universal shape of the thickness profile along the bridge. The coalesced fractures then transition into a single fracture at late times. Finally, we discuss a number of other interesting scenarios that may occur such as, non-coalescing fractures, asymmetric coalescence and ridge formation.