Flotation is a complex, multiphase process used to separate minerals. Four problems central to the fundamentals of the flotation process were studied. A multiphase grid turbulence experiment was conducted to verify particle collision models. The slip velocities of solid particles and bubbles were measured using Digital Particle Image Velocimetry (DPIV). The experimental results were compared with the predictions from empirical and theoretical collision models. Time-resolved DPIV was used to measure the turbulent velocity field in a Rushton turbine around the impeller region. The turbulence quantities were found by removing the periodic component from the blade passing, which is a dominant part of the measured velocities near the impeller. We provide evidence that larger, biased dissipation and turbulent kinetic energy values are estimated in the vicinity of the impeller due to the periodic component of the blade passage. The flow was found to be anisotropic close to the impeller. Vortex detection revealed that the tip vortices travel in a nearly radial direction from the impeller for small Reynolds numbers and with a wider distribution for higher Reynolds numbers. The rise of a buoyant bubble and its interaction with a free liquid surface was experimentally investigated using Time-Resolved Digital Particle Image Velocimetry as a function of bubble size, and surfactant concentration of the fluid medium. It is shown that the presence of a surfactant significantly affected the characteristics of the velocity field during the rise and interaction with the free surface. This difference is attributed to the adsorption coverage of the surfactant at the bubble-fluid interface. Wake profiles were compared. The presence of large vortices were observed and found to play a significant role. Finally, Numerical and experimental results of stable and unstable foams are presented by comparing liquid fractions and bubble sizes. There was good agreement between the experiments and numerical modeling in free drainage and forced drainage experiments. In addition, foam coarsening was measured and characterized experimentally. Each of the problems investigated have added to the understanding in the underlying physics of the flotation process and can lead to more accurate modeling. The ultimate goal of this work is to contribute to the design of more effective and efficient flotation machines. / Ph. D.

Les propriétés acoustiques des bulles sont reconnues pour leur potentiel dans des applications tant biologiques que médicales. Capables de provoquer la lyse des cellules en générant des écoulements intenses, elles peuvent aussi servir d'agent de contraste en échographie.Ce manuscrit traite de la dynamique de vibration de bulles confinées entre les deux murs d'un canal microfluidique. Ces bulles exhibent une pulsation en volume aux faibles amplitudes d'excitation, à laquelle se superpose un mode de surface paramétrique aux plus fortes amplitudes. Le matériau constituant le canal étant élastique, la pulsation de la bulle confinée a pour effet de générer des ondes de Rayleigh sur les parois du canal. Grâce à ces ondes de surface, les bulles vont pouvoir se coupler les unes aux autres. Ce couplage a un effet sur les écoulements hydrodynamiques autour de ces bulles. En effet, la présence d'une bulle voisine engendre l'apparition d'un mode de translation de la bulle qui, couplé à sa pulsation en volume, conduira à la génération d'écoulements à longue portée. Ce même couplage permet aux bulles de s'auto-organiser en réseau. Afin d'étudier de manière contrôlée les effets collectifs des bulles, leur position a été fixée à l'aide de puits capillaires. Les conditions d'amplification et de synchronisation de la vibration des bulles sont recherchées en vue de créer de nouveaux méta-matériaux. / The pulsation properties of air bubbles under ultrasound have received much attention since the development of sonoporation and contrast agents. Spherical bubbles are well known to induce streaming when excited by ultrasound.We report in this manuscript the acoustic vibration of microbubbles confined between the two walls of a microfluidic channel. These bubbles exhibit a volumetric pulsation at low intensities of ultrasound, superimposed with a parametric surface mode for higher intensities of the pressure field. Because the channel walls are elastic, the bubble pulsation leads to the generation of Rayleigh waves at the channel wall interface. The bubble coupling induced by these surface waves has hydrodynamic consequences. In fact, a neighbouring bubble will create a translation mode of the bubble, in addition to its volumetric pulsation. It gives rise to a long-range mixed-mode streaming. The Rayleigh waves lead also to a self-organization of the bubbles in a network. In order to study the collective effects of these bubble networks in a controlled manner, bubble positions were fixed by capillarity on micropits. Conditions for an amplification or a synchronization of the bubble pulsations are sought in order to develop new bubble metamaterials.

Pour assurer le transport de la sève des racines vers les feuilles, les plantes vasculaires génèrent de très fortes dépressions dans le liquide, pouvant atteindre -200 bar, au niveau des feuilles. Cette dépression « tire » sur la colonne d'eau contenue dans l'appareil vasculaire de l'arbre. La cohésion de l'eau maintient la sève sous forme liquide. Cet état métastable peut se rompre : des bulles de cavitation apparaissent. Elles créent un « bouchon » d'air dans le réseau hydraulique de la plante et gênent la circulation de la sève. C'est ce que l'on appele l'embolie. Si ce phénomène se généralise, il peut provoquer la mort de la plante.Ce travail de thèse est consacré à 'invasion d'air dans des réseaux hydrauliques naturels ou artificiels initialement à pression négative. Nous avons d'abord étudié l'embolie dans les feuilles. Nous avons développé une technique novatrice permettant de relever la propagation spatiale de l'embolie dans le réseau hydraulique des feuilles. Nous montrons que l'embolie, quelque soit l'espèce, se propage par à-coups des plus grosses nervures aux plus petites.Afin de comprendre les lois physiques sous-jacentes, nous utilisons deux systèmes modèles. Nous réalisons d'abord des réseaux artificiels dans un hydrogel reproduisant les caractéristiques de la circulation de la sève ascendante. Après la relaxation de la tension dans le réseau par l'apparition de la bulle, nous observons des oscillations de surface et une croissance lente de la bulle, liée à l'évacuation de l'eau à travers l'hydrogel. Cette croissance peut atteindre un régime quasi-stationnaire. Ce systèmes ne nous permettant pas de reproduire toutes les caractéristiques géométriques du xylème, nous présentons une modélisation informatique reposant sur l'analogie entre réseaux hydrauliques et électrocinétique. Nous reproduisons les caractéristiques du xylème dans lequel circule la sève : les éléments conducteurs sont reliées par les ponctuations, des valves protégeant la plante de l'embolie. Nous retrouvons les à-coups caractéristiques de la propagation de l'embolie dans les feuilles.Enfin, nous discutons l'application des résultats précèdents dans le cas du bois et nous présentons quelques résultats obtenus sur du pin sylvestre. / To assure the transport from the roots to the leaves, vascular plants create strong depressions in the sap, next to -200 bars. This depression pulls the water column contained by the tree vascular system. The water cohesion keeps the sap under liquid state. This metastable state can breaks: cavitation bubbles appear. They create an air plug inside the plant hydraulic network and impede sap flow. This phenomena called embolism could lead to the plant death by preventing the sap transport.This thesis is dedicated to the air invasion into hydraulics networks under negative pressure. First, we study the leaf embolism. We developed a new technique which allows us to record the spatial propagation of embolism in leaves hydraulic network. We show that the embolism propagates by steps from biggest veins to smallest veins.Next, in order to understand the underlying physical laws, we use two model systems. We build artificial networks in a hydrogel which mimics the sap flow characteristics. After the relaxation of the negative pressure in the network by the nucleation of a bubble, we observe surface oscillations and the slow growth of the bubble. This growth is linked to the water transport through the hydrogel and can reach a stationary regime.As we are not able to reproduce all the characteristics of the leaf network with the hydrogel, we create a computer modeling based on the Ohm analogy between hydraulics networks and electrical circuits. We reproduce the specific features of the xylem which transport the sap: the conduits are linked by pits, small valves which limit the progression of the embolism. We were able to recover the distinctiveness steps in embolism.Finally, we discuss the application of the preceding results to wood and we present some results on Pinus sylvestris.

Bubbly turbulent flows occur in a variety of industrial, naval and geophysical problems. In these flows, the bubbles in the flow interact with turbulence and/or vortical structures present in the continuous phase, resulting in bubble motion and deformation, and at the same time modifying the turbulence and/or vortical structures. Despite the fact that this has been a subject of interest for some time, mechanisms of bubble break-up due to turbulence and turbulence modulation due to bubbles are not well understood. To help understand this two-way coupled problem, we study in this thesis, the interaction of single and multiple bubbles with vortical structures; the thesis being broadly divided in to three parts. In the first part, we study the interaction of a single bubble with a single vortical structure, namely a vortex ring, formed in the continuous phase (water). This may be thought of as a simplified case of the interaction of bubbles with vortical structures in any turbulent flow. We then increase the complexity and study the interaction of a single bubble with naturally occurring vortical structures present in a fully developed turbulent channel flow, and then finally to the case of a large number of bubbles injected in to a fully developed turbulent channel. The bubble motions and deformations in all three cases are directly imaged using high speed visualizations, while the flow field information is obtained using time-resolved Particle-Image Velocimetry (PIV) in the first two cases, and from pressure drop measurements within the channel in the latter case. The interaction of a single vortex ring with a bubble has been studied for a large range of vortex ring strengths, represented in terms of a Weber number (We). We find that in all cases, the bubble is first captured by the low pressure within the core of the ring, then stretched azimuthally within the core, and gradually broken up in to a number of smaller bubbles. Along with these bubble deformations, the vorticity within the core of the ring is also modified significantly due to bubble capture. In particular, at low We, we find that the core of the ring fragments as a result of the interaction resulting in a large reduction in the enstrophy of the ring and its convection speed. In the second part of the thesis, interaction of a single bubble with naturally occurring vortical structures present in a fully developed turbulent channel is studied. In this case, single bubbles of different sizes are injected either from bottom or top wall into a channel at Reynolds number of about 60,000. We study the trajectories of the single bubble, and also investigate the effect that such bubbles have on the naturally occurring vortical structures present in these flows. The injected bubble is found to have three broadly different types of bubble paths when injected from the bottom wall, which are sliding along the wall, bouncing motions and vertical escape from the vicinity of the wall. Even at the same bubble diameter Db and channel flow Re, we find that different realizations show considerable variations, with all three bubble paths being possible. PIV measurements of a bubble captured by a naturally occurring vortical structure in the flow, shows a more rapid decrease in enstrophy compared to naturally occurring structures in the absence of bubbles, as seen in the interaction of a bubble with a vortex ring. We also find that the bubble can interact with multiple vortical structures, depending on their strength and spatial distribution in the flow, resulting in a complex bouncing bubble motion. In the third part of the study, a large number of bubbles are injected in to the channel through porous plates fixed at the top and bottom channel walls. The main parameters here are the channel Re, bubble void fraction (α) and the orientation of injection. In this case, in addition to bubble visualizations, the pressure drop through the channel is measured at different vertical locations. These measurements show large vertical variations in the measured pressure drop due to the presence of bubbles. The overall drag reduction in these cases is obtained from an integral of the pressure drop variation along the vertical direction. The visualizations show a number of bubble dynamics regimes depending on the parameters, with possibilities of both increased and decreased drag compared to the reference no bubble case. From simultaneous measurements, we relate the variations in drag reduction to the different bubble dynamics regimes. We find that at the same void fraction (α), the drag reduction obtained can be very different due to changes in bubble dynamics regimes caused by changes in other parameters. Top wall injection is observed to give good drag reductions over a wide range of flow Re and α, but is seen to saturate beyond a threshold α. In contrast, the bottom wall injection case shows that drag reduction continuously increases with αat high Re. The present study shows a maximum of about 60% increase and a similar 60% reduction in wall drag over the entire range of conditions investigated.

<div>With the rapid development of the advanced two-phase flow experimental technologies, more experimental databases with extended measurement ranges have been established to support the two-phase flow model development. The advantage of the Two Fluid model in modeling the complex two-phase flow phenomena over the mixture models stands out. One key aspect in the Two Fluid model development is the accurate modeling of the interfacial area between phases, which is strongly related to the interfacial mass, momentum, and energy transfer. As a closure relation of interfacial area concentration (interfacial area per unit volume) for the Two Fluid model, the Interfacial Area Transport Equation (IATE) provides dynamic predictions on the interfacial area change. It substantially solves the shortcoming of using flow-regime-dependent empirical correlations that can introduce numerical discontinuities between flow regimes. </div><div><br></div><div>The IATE has been extensively developed over the past twenty-five years. Many studies targeted on improving its prediction capability by developing bubble interaction source terms based on their experimental data. </div><div>The existing models are usually based on medium and large flow channels, yet the models may not be physically fit the small flow channels. The major reason is that the wall effect can have a larger influence on the two-phase flow in a small flow channel, as the surface area to volume ratio greatly increases. Therefore, the primary objectives of this study are to physically investigate the wall effect on two-phase flow and develop a generalized IATE by extending the application range of existing IATE from large and medium flow channels to small flow channel.</div><div><br></div><div>To achieve the objective, this study established a rigorous database of air-water two-phase flows in a small diameter pipe with its inner diameter of 12.7 mm, focusing on the bubbly-to-slug transition regime. The experimental analysis was performed on the pipe wall effect on the interfacial characteristics, based on the current experimental database and the existing experimental database collected on vertical pipes of different sizes. It is observed that 1) the pipe wall effect can alter the non-uniform radial two-phase distribution; 2) the bubbly-to-slug flow regime transition in a small diameter pipe happens in a smaller void fraction than in a large diameter pipe; 3) the bubble coalescence phenomenon can be more dominant for small pipe flow, and an intensive intergroup transfer can happen for the two-group interfacial area transport in two-phase flows. </div><div>As the interfacial area transport is directly related to the two-phase geometrical configuration, the two-phase geometrical parameters, void fraction and relative bubble size, are identified as the key parameters for modeling.</div><div><br></div><div>In the modeling of IATE source terms, the high geometrical scalability of the model is realized by properly including the wall effect into the modeling consideration. The following major improvements on the existing models are: 1) the inertia subrange assumption on the turbulent-driven interaction is properly improved; 2) the bubble-induced turbulent-driven interactions such as wake entrainment is revised by considering the wall effect on the wake region. In summary, models of bubble interaction due to random collision, wake entrainment, turbulent impact, and shearing-off are revised based on the existing studies on the IATE source terms development. The newly proposed interfacial area transport models are evaluated against an experimental database with 112 test conditions in total from a wide range of experimental pipe diameters from 12.7 mm to 304.8 mm. The new models can accurately capture the drastic intergroup transfer of void fraction and interfacial area concentration between two groups in transition flows. Overall, the relative error of void fraction and interfacial area concentration comparing with the experimental data are within ±15\% and ±10\%, respectively.</div>

This dissertation develops a computational method for simulating laser-induced cavitation and investigates the mechanism behind the formation of non-spherical bubbles induced by long-pulsed lasers. The proposed computational method accounts for the laser emission and absorption, phase transition, and the dynamics and thermodynamics of a two-phase fluid flow. In this new method, the model combines the Navier-Stokes (NS) equations for a compressible inviscid two-phase fluid flow, a new laser radiation equation, and a novel local thermodynamic model of phase transition. The Navier-Stokes equations are solved using the FInite Volume method with Exact two-phase Riemann solvers (FIVER). Following this method, numerical fluxes across phase boundaries are computed by constructing and solving one-dimensional bi-material Riemann problems. The new laser radiation equation is derived by customizing the radiative transfer equation (RTE) using the special properties of laser, including monochromaticity, directionality, high intensity, and a measurable focusing or diverging angle. An embedded boundary finite volume method is developed to solve the laser radiation equation on the same mesh created for the NS equations. The fluid mesh usually does not resolve the boundary and propagation directions of the laser beam, leading to the challenges of imposing the boundary conditions on the laser domain. To overcome this challenge, ghost nodes outside the laser domain are populated by mirroring and interpolation techniques. The existence and uniqueness of the solution are proved for the two-dimensional case, leveraging the special geometry of the laser domain. The method is up to second-order accuracy, which is also proved, and verified using numerical tests. A method of latent heat reservoir is developed to predict the onset of vaporization, which accounts for the accumulation and release of latent heat. In this work, the localized level set method is employed to track the bubble surface. Furthermore, the continuation of phase transition is possible in laser-induced cavitation problems, especially for long-pulsed lasers. A method of local correction and reinitialization is developed to account for continuous phase transitions. Several numerical tests are presented to verify the convergence of these methods. This multiphase laser-fluid coupled computational model is employed to simulate the formation and expansion of bubbles with different shapes induced by different long-pulsed lasers. The simulation results show that the computational method can capture the key phenomena in the laser-induced cavitation problems, including non-spherical bubble expansion, shock waves, and the ``Moses effect''. Additionally, the observed complex non-spherical shapes of vapor bubbles generated by long-pulsed laser reflect some characteristics (e.g., direction, width) of the laser beam. The dissertation also investigates the relation between bubble shapes and laser parameters and explores the transition between two commonly observed shapes -- namely, a rounded pear-like shape and an elongated conical shape -- using the proposed computational model. Two laboratory experiments are simulated, in which Holmium:YAG and Thulium fiber lasers are used respectively to generate bubbles of different shapes. In both cases, the predicted bubble nucleation and morphology agree reasonably well with the experimental observation. The full-field results of laser radiance, temperature, velocity, and pressure are analyzed to explain bubble dynamics and energy transmission. It is found that due to the lasting energy input, the vapor bubble's dynamics is driven not only by advection, but also by the continued vaporization at its surface. Vaporization lasts less than 1 microsecond in the case of the pear-shaped bubble, compared to over 50 microseconds for the elongated bubble. It is thus hypothesized that the bubble's morphology is determined by a competition between the speed of bubble growth due to advection and continuous vaporization. When the speed of advection is higher than that of vaporization, the bubble tends to grow spherically. Otherwise, it elongates along the laser beam direction. To test this hypothesis, the two speeds are defined analytically using a model problem and then estimated for the experiments using simulation results. The results support the hypothesis and also suggest that when the laser's power is fixed, a higher laser absorption coefficient and a narrower beam facilitate bubble elongation. / Doctor of Philosophy / Laser-induced cavitation is a process where laser beams create bubbles in a liquid. This phenomenon is widely applied in research and microfluidic applications for precise control of bubble dynamics. It also naturally occurs in various laser-based processes involving liquid environments. Understanding laser-induced cavitation is important for enhancing the effectiveness and safety of related technologies. However, experimental studies encounter limitations, highlighting the development of numerical methods to advance the understanding of laser-induced cavitation. The laser-induced cavitation can be roughly described as localized boiling through thermal radiation. The detailed physics involves the absorption of laser light by a liquid, the formation of vapor bubbles due to localized heating, and the dynamics of both the bubbles and the surrounding liquid. The first part of the dissertation introduces a new computational method for modeling these phenomena. The dynamics of the two-phase flow are modeled by the Navier-Stokes equations, which are solved using the FInite Volume method with Exact two-phase Riemann solvers (FIVER). The absorption of the laser light is modeled by a new laser radiation equation, which is derived from laser energy conservation and special properties of the laser. An embedded boundary finite volume method is developed to solve this equation on the same mesh created for the NS equations. Additionally, a method of latent heat reservoir is developed to predict the onset of vaporization. In this work, the level set method is employed to track the bubble surface, and a method of local correction and reinitialization is developed to account for possible continuous phase transitions. After developing this new method, several test cases are simulated. The simulation results show that the method can capture the key phenomena in the laser-induced cavitation problems, including the absorption of laser light, non-spherical bubble expansion, and shock waves. When the laser pulse is comparable to or longer than the acoustic time scale (long-pulsed laser), vapor bubbles generated often have complex non-spherical shapes. The bubble shapes reflect some characteristics (e.g., direction, width) of the laser beam. The second part of the dissertation investigates the relation between bubble shapes and laser parameters. Two laboratory experiments are simulated, in which two different lasers are used to generate bubbles of different shapes, namely, a rounded pear-like shape and an elongated conical shape. In both cases, the simulated bubbles exhibit shapes and sizes that reasonably match the experimental results. The simulation results of temperature, pressure, and velocity fields are analyzed to explain bubble dynamics and energy transmission. The analysis shows that the expansion of bubbles induced by long-pulsed lasers is determined not only by advection but also by the continued vaporization at its surface. Vaporization lasts less than $1$ microsecond in the case of the pear-shaped bubble, compared to over $50$ microseconds for the elongated bubble. It is thus hypothesized that the bubble expansion is determined by a competition between the speed of bubble growth due to advection and continuous vaporization. When the speed of advection is higher than that of vaporization, the bubble tends to grow spherically. Otherwise, it elongates along the laser beam direction. To test this hypothesis, the two speeds are defined analytically using a model problem and then estimated for the experiments using simulation results. The results support the hypothesis and also suggest that when the laser's power is fixed, a higher laser absorption coefficient and a narrower beam facilitate bubble elongation.

No description available.

Ce travail de recherche est dédié à la compréhension des mécanismes physiques de l’érosion de cavitation dans un fluide compressible à l’échelle fondamentale de l’implosion d’une bulle de cavitation. Suite à l’implosion d’une bulle de vapeur à proximité d’une surface solide, des très hautes pressions sont générées. Ces pressions sont considérées responsables de l’endommagement (érosion) des surfaces solides observé dans la plupart des applications. Notre approche numérique démarre avec le développement d’un solveur compressible capable de résoudre les bulles de cavitation au sein du code volumes finis YALES2 en utilisant un simple modèle de mélange homogène des phases fluides. Le solveur est étendu à une approche ALE (Arbitraire Lagrangien Eulérien) dans le but de mener des simulations d’interaction fluide-structure sur un maillage mobile. La réponse du matériau solide est calculée avec le code de calcul éléments finis Cast3M, et nous a permis de mener des simulation avec un couplage d’abord monodirectionnel, ensuite bidirectionnel, entre le fluide et le solide. On compare des résultats obtenus à deux dimensions, puis à trois, avec des observations expérimentales. On discute les chargements de pression estimés, et les réponses de différents matériaux pour des implosions de bulle à des différentes distances de la surface. Enfin, à travers l’utilisation de simulations avec couplage bidirectionnel entre fluide et solide, on identifie l’amortissement des chargements de pression pour les différents matériaux. / This research is devoted to understanding the physical mechanism of cavitation erosion in compressible liquid flows on the fundamental scale of cavitation bubble collapse. As a consequence of collapsing bubbles near solid wall, high pressure impact loads are generated. These pressure loads are believed to be responsible for the erosive damages on solid surface observed in most applications. Our numerical approach begins with the development of a compressible solver capable of resolving the cavitation bubbles in the finite-volume solver YALES2 employing a simplified homogenous mixture model. The solver is extended to Arbitrary Lagrangian-Eulerian formulation to perform fluid structure interaction simulation with moving mesh capabilities. The material response is resolved with the finite element solver Cast3M, which allowed us to perform one-way and two-way coupled simulations between the fluid and solid domains. In the end, we draw comparisons between 2D and 3D vapor bubble collapse dynamics and compare them with experimental observations. The estimated pressure loads on the solid wall and different responses of materials for attached and detached bubble collapses are discussed. Finally, the damping of pressure loads by different materials is identified with two-way coupled fluid-structure interaction.

A cavitação e a dinâmica de bolhas são tópicos bastante recorrentes na literatura, devido sobretudo a seus efeitos em diversos tipos de fenômenos, como transferência de calor e escoamento em tubos. Considerando fases líquidas, sabe-se que estas estruturas de cavidade estão normalmente associadas ao equilíbrio metaestável, alcançado devido a quedas locais de pressão ou ao superaquecimento de uma substância pura (ou quase). Nestes casos é necessária a inicialização da mudança de fase através de algum mecanismo adequado, o qual gera uma sequência rápida de fenômenos. Apesar de comumente associado a danos, recentemente vários estudos vêm mostrando aplicações práticas deste tema, além de um campo ainda pouco explorado, que é o das macro cavidades. Essas cavidades podem ser geradas através do aquecimento de água a baixa pressão, sob condições específicas, criando sequências explosivas e formando movimentos como pistão para a água no interior de um invólucro convenientemente dimensionado. Este fenômeno mostra-se semelhante em diversos aspectos às micro cavidades, mais especificamente às cavidades próximas a superfícies livres, embora, sem dúvida, em escala muito maior. Os aspectos mencionados foram filmados com câmeras de alta velocidade e as características observadas foram comparadas com aquelas observadas em micro escala. Vários testes foram desenvolvidos de forma a melhor entender a dinâmica da formação e colapso dessas estruturas, sobretudo levando em conta um comportamento mais unidimensional para a evolução da bolha. Através de várias aproximações e análise de diferentes hipóteses para a variação de pressão e para a força de resistência, soluções analíticas e numéricas foram obtidas para a força exercida no fundo do contêiner e para a expansão e colapso das bolhas ao longo do tempo. As soluções propostas, em comparação com os dados experimentais, mostraram boa concordância entre si, sugerindo que os aspectos fundamentais da dinâmica da cavidade foram devidamente considerados e quantificados. / Cavitation and bubble dynamics are fairly recurring topics in literature, mostly due to their effects in various types of phenomena such as heat transfer and flow in pipes. Considering liquid phases, it is known that these cavity structures are normally associated with the metastable equilibrium, reached due to local pressure drop or overheating of a pure substance (or nearly so). In these cases, the phase change require a startup via some appropriate mechanism, which generates a fast sequence of phenomena. Although commonly associated with damage, recently several studies shown practical applications of these topics, and a still little explored field emerged, which is the field of macro cavities. These cavities can be generated by heating water at a low pressure, under specific conditions, creating an explosive sequences and forming piston like movements for the water inside a properly scaled casing. This phenomenon appears to be similar in many aspects to micro cavities, more specifically for cavities near free surfaces, although, without doubt, on a much larger scale. The mentioned aspects were filmed with high-speed cameras and the main features were compared with those observed in micro scale. Several tests have been developed to better understand the dynamics of the formation and collapse of these structures, especially taking into account a more one-dimensional behavior to the evolution of the bubble. Through various approximations, and analysis of different assumptions for the variation of pressure and the resistance force, analytical and numerical solutions were obtained for the force exerted on the bottom of the container and the expansion and collapse of bubbles over time. The proposed solutions in comparison with experimental data showed good agreement between each other suggesting that the fundamental aspects of the dynamics of the cavity were properly considered and quantified.

Nous étudions les comportements dynamiques de solutions aqueuses de dioxyde de carbone, pures ou sous forme de boissons gazeuses. Nous observons les façons dont des solutions carbonatées, initialement à l'équilibre de Henry, répondent à une perturbation, qui peut être un changement brusque de pression ou une agitation mécanique. Ces questions sont examinées expérimentalement, à l'aide de dispositifs construits pour cette étude. Ceux ci permettent de visualiser les champs de vitesse et les fronts de dissolution dans le fluide, dans des conditions variées de pression, taille et forme de système. Une partie importante est consacrée à la chemi-convection provoquée par la déstabilisation d'une couche diffuse de CO2 dissout. Nous présentons une caractérisation complète du phénomène, et une interprétation basée sur une théorie de l'instabilité de Rayleigh-Taylor correspondante. L'autre partie de notre travail concerne des systèmes fermés, dont la bouteille de champagne est l'exemple type. Nous montrons que l'agitation de la bouteille provoque une légère baisse transitoire de la pression interne, et expliquons le phénomène à l'aide d'un modèle basé sur la théorie d'Epstein-Plesset de la dynamique des bulles. / This work is about dynamical phenomena of water-carbon dioxide solutions, either pure binary mixtures or carbonated beverages. We address the general problem of how such solutions, initially at Henry's equilibrium, respond to a perturbation. The latter may be a sudden change in pressure, or mechanical shaking. These problems are investigated with the help of especially designed experimental hardware that allows us to visualize the velocity field and the concentration front inside solutions, in diverse conditions of pressure, system size and shape. An important part of the work is dedicated to chemi-convection, i.e. the fluid motion induced by destabilisation of the diffuse layer of dissolved CO2. Both experimental characterization and interpretation through a theory of the corresponding Rayleigh-Taylor instability are presented. The other part of the work is related to closed systems, representative of a bottle of champagne and of sodas in general. A key observation is that shaking produces a small transient drop of the internal pressure, which we explain through a dedicated modelbuilt on Epstein-Plesset's theory of bubble dynamics.