It can be shown that for the complete description of all the physical parameters in the flow behind an imtermediate strength unsteady shock, a knowledge of the particle trajectories within the flow is sufficient. This principle has been applied to determine the variation of the physical parameters throughout the length of a conventional shock tube. The particle trajectories were obtained by the high speed photography of cigarette smoke tracers, placed at 10 cm. intervals along the tube. By applying the conservation of mass equation to the particle trajectory data, the density variation was obtained throughout the flow including the rarefaction wave from the end of the compression chamber and behind the first reflected shock from the closed end of the expansion chamber. By means of the Rankine-Hugoniot relation, the pressures immediately behind the incident and reflected shock fronts were calculated, and by assuming isentropic flow between shocks along any particle trajectory, the complete pressure variation was determined. The temperature and local sound speed were subsequently calculated at all points and the particle velocities were determined from the time derivative of the particle trajectories. A complete mapping of all the parameters in the shock tube was thus obtained using a single photographic technique, which is simpler than previous methods. / Graduate / 0605

There is a long terms of developement for academics theoretical analyzing and experimental researching by using the Lagrangian method. But for such trajectory experimentalists still have interference with reflected waves because of the length of the water tank is too short or the diameter and the density of the simulate particle , in spite of measuring the trajectory of the fluid particle have done. For there is no quite completed quantification data for the trajectory of fluid particle, this study is aiming at researching the truly movement of the flow field under wave-current interaction by trajectory measuring. This research choosing the simulate particle¡¦s diameter for 1 mm , collocating with a high-speed vedio camera to record the particle¡¦s moving characteristics while the wave-current interaction occured, to proceed a series of qualitative and quantitative testing. And to comple with all these data and improve the modification by using Image Processing to derive and orientate the coordinates . According to the experimental results of the flow field,it has proved that mass transport occured at the same-depth and no-flow condition through the wave progressing direction.The trajectory of the fluid particle of wave-current interaction in co-flow , its curve presenting the cross-convolution increasing and even presenting the cuspidal locus. And the trajectory of the fluid particle of wave-current interaction in inverse ¡Vflow is opposite to the trajectory of the no-flow movement. The results of the experiment is quite accord with to the 3rd order the theoretical analyzing of Chen ¡]1994¡^and Shu¡BChen¡]2006¡^¡CThe fluid particle reproducting the moving period of the high-elevation is greater than the wave¡¦s and increasing by the sharpness of the wave. The mass transport velocity is the same theory results ,and decreased deviation of artificiality in estimating particle position. According to the ratio of the experimental results, root mean square of error Ex and total mass transport displacement. The experimental results compared to the theoretical results obtained by Chen (1994)and Hsu¡BChen(2006) has the similar results as well.

A system for recording the trajectories of non-planar shocks and particle tracers within a shock tube flow has been developed. The optics consists of a double-pass schlieren system with a multiply pulsed ruby laser as light source. The laser is synchronized with a high speed framing camera. A grid of ammonium chloride tracers is injected into the flow field, and the motion of the tracers behind the Mach reflection of intermediate strength shocks has been recorded. Analysis of the trajectories has yielded the space and time variation of the physical properties within the flow field. / Graduate / 0605

The physical properties within the two-dimensional flow produced by the reflection of a plane shock of intermediate strength at a wedge, have been determined by analysis of the particle trajectories. The particle trajectories were obtained by high speed photography of smoke tracers within the flow. Trajectories were determined for different initial positions of the tracers relative to the wedge. The conservation of mass equation was used to determine the density at points within the flow. A knowledge of the shock configurations within the flow, together with the Rankins-Hugoniot equation, was used to determine the pressure immediately behind the incident and reflected shocks. The isentropic equation of state was used to determine the pressure after the passage of the reflected shock. The pressure determined in this manner agreed, within the limits of experimental error, with that obtained using a piezo-electric transducer. The temperature, velocity of sound, and particle velocity at points within the flow were also determined. / Graduate / 0605

No description available.

The majority of literature regarding the numerical simulation of arc discharges in gaseous environments has used a plasma physics approach. Virtually all simulations treat the discharge as an idealized gaseous plasma, which can be described by temperature, pressure, and electric field. This approach can work well if the media is a shielding gas such as Argon; however, the approach does not work well for processes such as underwater welding, EDM, and underwater discharges used to generate high purity particles. The reason these discharges do not have many extensive simulation efforts as described in the literature is because they occur in liquid dielectric media (Oil and water) which complicates the simulation efforts. Most research efforts in these areas describe experimental methods to evaluate discharge properties In this research a new method to investigate discharges in a dielectric media using an electrostatic and particle physics approach is proposed and validated. A commercial code that has been developed to simulate charged particle beams, dielectric materials, and perform multi-physics analyses, is the Vector Fields suite of solvers from Cobham Technical Services. This research demonstrates a simulation methodology that can be used to simulate a DC electric arc discharge in a lossy dielectric media using the Vector Fields environment. This simulation is the first of its kind to simulate this type of a discharge with a commercial FEA code. As such there are some limitations to the simulation. However, the simulation can be used to investigate the following: 1.Any metal, electrode geometry, discharge gap, or dielectric media can be studied 2.Primary Beam Physics – Electron velocity/acceleration (direct calculation of electron temperature) – Energy deposition on the anode from all emission sources – Effect of dielectric media on beam physics (trajectories, velocity, constriction, beam induced magnetic fields, space chare, and secondary emission) – Beam current – Particle trajectories (including relativistic effects) 3. Secondary Particle Generation and physics – Atomic species (neutral particles or ions) and secondary electron emission – Particle trajectories – Back ion bombardment on the cathode

Examples of superhydrophobic surfaces found in nature such as self-cleaning property of lotus leaf and walking on water ability of water strider have led to an extensive investigation in this area over the past few decades. When a water droplet rests on a textured surface, it may either form a liquid-solid-vapor composite interface by which the liquid droplet partially sits on air pockets or it may wet the surface in which the water replaces the trapped air depending on the surface roughness and the surface chemistry. Super water repellent surfaces have numerous applications in our daily life such as drag reduction, anti-icing, anti-fogging, energy conservation, noise reduction, and self-cleaning. In fact, the same concept could be applied in designing and producing surfaces that repel organic contaminations (e.g. low surface tension liquids). However, superoleophobic surfaces are more challenging to fabricate than superhydrophobic surfaces since the combination of multiscale roughness with re-entrant or overhang structure and surface chemistry must be provided. In this study, simple, cost-effective and potentially scalable techniques, i.e., airbrush and electrospray, were employed for the sake of making superhydrophobic and superoleophobic coatings with random and patterned multiscale surface roughness. Different types of silicon dioxide were utilized in this work to in order to study and to characterize the effect of surface morphology and surface roughness on surface wettability. The experimental findings indicated that super liquid repellent surfaces with high apparent contact angles and extremely low sliding angles were successfully fabricated by combining re-entrant structure, multiscale surface roughness, and low surface energy obtained from chemically treating the fabricated surfaces. In addition to that, the experimental observations regarding producing textured surfaces in mask-assisted electrospray were further validated by simulating the actual working conditions and geometries using COMSOL Multiphysics.

Le but de cette thèse est d'étudier le transport et le dépôt de particules solides dans les écoulements à travers les fractures. Dans un premier temps, l'écoulement monophasique à travers les fractures est étudié afin d'évaluer la validité de la loi cubique locale comme modèle de l'écoulement. Des canaux à parois sinusoïdales à géométrie variable sont utilisés pour représenter différents types de fractures. Un premier développement analytique montre que l'ouverture hydraulique de la fracture diffère de son ouverture moyenne lorsque la rugosité des parois est élevée. La méthode des éléments finis est ensuite utilisée pour résoudre les équations de continuité et de Navier-Stokes et comparer les solutions numériques aux prédictions théoriques de la loi cubique locale sur une gamme relativement étendue de nombres de Reynolds Re. Pour de faibles Re, typiquement inférieurs à 15, la loi cubique locale décrit raisonnablement l'écoulement, surtout lorsque la rugosité et le déphasage entre les parois sont relativement faibles. Dans un deuxième temps, les écoulements chargés de particules sont étudiés. Une approche analytique est d'abord développée pour montrer comment des particules distribuées dans un écoulement stationnaire et laminaire à travers une fracture peuvent être transportées sur de longues distances ou au contraire se déposer à l'intérieur. Plus précisément, une équation simple décrivant la trajectoire d'une particule est établie. Sur la base de cette équation, il est démontré que, quand l'inertie des particules est négligeable, leur comportement dépend directement de la géométrie de la fracture et d'un nombre adimensionnel W qui relie la vitesse de sédimentation des particules à la vitesse moyenne de l'écoulement. L'équation proposée est vérifiée en comparant ses prédictions à des simulations numériques de suivi de particules prenant en compte l'inertie des particules et résolvent complètement les équations de Navier-Stokes. Il est montré que l'équation est valide lorsque l'inertie du fluide est faible. Des diagrammes de régimes, permettant de prévoir le comportement des particules à travers la fracture sont proposés. Enfin, un appareil expérimental conçu dans le but d'effectuer une évaluation pratique du modèle analytique est présenté et les résultats préliminaires sont discutés. Les résultats expérimentaux préliminaires tendent valider le modèle analytique. De façon plus générale, les résultats obtenus à travers ce travail de thèse font progresser nos connaissances du comportement des petites particules transportées dans les écoulements de fractures. Potentiellement, ce travail devrait permettre d'améliorer notre prévision de la pollution souterraine, et peut avoir des applications dans le développement de nouvelles techniques de filtration de l'eau et de séparation des minéraux / The aim of the present thesis is to study the transport and deposition of small solid particles in fracture flows. First, single-phase fracture ow is investigated in order to assess the validity of the local cubic law for modeling ow in corrugated fractures. Channels with sinusoidal walls having different geometrical properties are considered to represent different fracture geometries. It is analytically shown that the hydraulic aperture of the fracture clearly deviates from its mean aperture when the walls roughness is relatively high. The finite element method is then used to solve the continuity and the Navier-Stokes equations and to simulate fracture ow in order to compare with the theoretical predictions of the local cubic law for Reynolds numbers Re in the range 0.067-67. The results show that for low Re, typically less than 15, the local cubic law can properly describe the fracture ow, especially when the fracture walls have small corrugation amplitudes. For Re higher than 15, the local cubic law can still be valid under the conditions that the fracture presents a low aspect ratio, small corrugation amplitude, and moderate phase lag between its walls. Second, particle-laden flows are studied. An analytical approach has been developed to show how particles sparsely distributed in steady and laminar fracture flows can be transported for long distances or conversely deposited inside the channel. More precisely, a rather simple particle trajectory equation is established. Based on this equation, it is demonstrated that when particles' inertia is negligible, their behavior is characterized by the fracture geometry and by a dimensionless number W that relates the ratio of the particles sedimentation terminal velocity to the ow mean velocity. The proposed particle trajectory equation is verified by comparing its predictions to particle tracking numerical simulations taking into account particle inertia and resolving the full Navier-Stokes equations. The equation is shown to be valid under the conditions that ow inertial effects are limited. Based on this trajectory equation, regime diagrams that can predict the behavior of particles entering closed channel flows are built. These diagrams enable to forecast if the particles entering the channel will be either deposited or transported till the channel outlet. Finally, an experimental apparatus that was designed to have a practical assessment of the analytical model is presented. Preliminary experimental results tend to verify the analytical model. Overall, the work presented in this thesis give new insights on the behavior of small particles in fracture flows, which may improve our prediction and control of underground contamination, and may have applications in the development of new water filtration and mineral separation techniques

La recherche sur le transport de sédiments dans les réservoirs vise principalement à optimiser la conception du réservoir dans les réseaux d’assainissement. La structure de l'écoulement, qui fait l’objet de cette recherche, représente le facteur principal de contrôle du mouvement des particules et conditionne leur dépôt. Le travail réalisé s’est basé aussi bien sur les méthodes numériques que les essais expérimentaux. La simulation numérique est traitée en utilisant trois géométries différentes, où un volume de modèle de fluide est appliqué pour le suivi de la surface libre et un modèle de phase discrète est utilisé pour calculer la trajectoire des particules, et une fonction définie par l'utilisateur basée sur la courbe de Shields est implémentée comme condition limite pour augmenter les taux de déposition simulés. Des séries d'expériences sont réalisées dans un réservoir rectangulaire avec une cavité, pour mesurer le champ de vitesses dans différentes conditions d’écoulement, et déterminer les zones de dépôts des sédiments au fond du réservoir. La comparaison entre les simulations numériques et les résultats expérimentaux montre une bonne concordance des résultats obtenus pour la prédiction des écoulements et des dépôts. L'amélioration du dépôt de particules nécessite une modification supplémentaire du modèle de suivi des particules. / The investigation on sediment transport in tanks is mainly for optimizing the design of tank in stormwater system and sewers. The flow pattern is the primary factor controlling the movement of particle. Therefore, the emphasis of this investigation is to determine the flow pattern and estimate the deposition of particle. Both computational fluid dynamics and experimental methods are applied to accomplish the research. Numerical simulation are processed by using three different geometries, where a volume of fluid model is applied for tracking the free-surface and a discrete phase model is used for calculation of particle trajectory, and an user defined function based on Shields curve is implemented to the boundary for improving the simulation on sedimentation. A series of experiments are carried out in a rectangular tank with a cavity, where velocity measurements are finished for experiments under different conditions and the sediment deposition is recorded. The comparison between numerical simulation and experimental results show better agreement in the prediction of flow, the improvement on particle deposition needs further modification in the particle tracking model.

De nos jours, la simulation des écoulements diphasiques a de plus en plus d’importance dans les chambres de combustion aéronautiques en tant qu’un des éléments requis pour analyser et maîtriser le processus complet de combustion, afin d’améliorer la performance du moteur et de mieux prédire les émissions polluantes. Dans les applications industrielles, la modélisation du combustible liquide trouvé en aval de l’injecteur sous forme de brouillard de gouttes polydisperse, appelé spray, est de préférence faite à l’aide de méthodes Eulériennes. Ce choix s’explique par les avantages qu’offrent ces méthodes par rapport aux méthodes Lagrangiennes, notamment la convergence statistique intrinsèque, le couplage aisé avec la phase gazeuse ainsi que l’efficacité pour le calcul haute performance. Dans la présente thèse, on utilise une approche Eulérienne basée sur une fermeture au niveau cinétique de type distribution Gaussienne Anisotrope (AG). L’AG résout des moments de vitesse jusqu’au deuxième ordre et permet de capter les croisements des trajectoires (PTC) à petite échelle de manière statistique. Le système d’équations obtenu est hyperbolique, le problème est bien-posé et satisfait les conditions de réalisabilité. L’AG est comparé au modèle monocinétique (MK) d’ordre 1 en vitesse. Il est approprié pour la description des particules faiblement inertielles. Il mène à un système faiblement hyperbolique qui peut générer des singularités. Plusieurs schémas numériques, utilisés pour résoudre les systèmes hyperboliques et faible- ment hyperboliques, sont évalués. Ces schémas sont classifiés selon leur capacité à traiter les singularités naturellement présentes dans les modèles Eulériens, sans perdre l’ordre global de la méthode ni rompre les conditions de réalisabilité. L’AG est testé sur un champ turbulent 3D chargé de particules dans des simulations numériques directes. Le code ASPHODELE est utilisé pour la phase gazeuse et l’AG est implémenté dans le code MUSES3D pour le spray. Les résultats sont comparés aux de simulations Lagrangiennes de référence et aux modèle MK. L’AG est validé pour des gouttes modérément inertielles à travers des résultats qualitatifs et quantitatifs. Il s’avère prometteur pour les applications complexes comprenant des PTC à petite échelle. Finalement, l’AG est étendu à la simulation aux grandes échelles nécessaire dans les cas réels turbulents dans le domaine industriel en se basant sur un filtrage au niveau cinétique. Cette stratégie aide à garantir les conditions de réalisabilités. Des résultats préliminaires sont évalués en 2D pour tester la sensibilité des résultats LES sur les paramètres des modèles de fermetures de sous mailles. / In aeronautical combustion chambers, the ability to simulate two-phase flows gains increasing importance nowadays since it is one of the elements needed for the full understanding and prediction of the combustion process. This matter is motivated by the objective of improving the engine performance and better predicting the pollutant emissions. On the industrial scale, the description of the fuel spray found downstream of the injector is preferably done through Eulerian methods. This is due to the intrinsic statistical convergence of these methods, their natural coupling to the gas phase and their efficiency in terms of High Performance Computing compared to Lagrangian methods. In this thesis, the use of Kinetic-Based Moment Method with an Anisotropic Gaussian (AG) closure is investigated. By solving all velocity moments up to second order, this model reproduces statistically the main features of small scale Particles Trajectories Crossing (PTC). The resulting hyperbolic system of equations is mathematically well-posed and satisfies the realizability properties. This model is compared to the first order model in the KBMM hierarchy, the monokinetic model MK which is suitable of low inertia particles. The latter leads to a weakly hyperbolic system that can generate δ-shocks. Several schemes are compared for the resolution of the hyperbolic and weakly hyperbolic system of equations. These methods are assessed based on their ability to handle the naturally en- countered singularities due to the moment closures, especially without globally degenerating to lower order or violating the realizability constraints. The AG is evaluated for the Direct Numerical Simulation of 3D turbulent particle-laden flows by using ASPHODELE solver for the gas phase, and MUSES3D solver for the Eulerian spray in which the new model is implemented. The results are compared to the reference Lagrangian simulation as well as the MK results. Through the qualitative and quantitative results, the AG is found to be a predictive method for the description of moderately inertial particles and is a good candidate for complex simulations in realistic configurations where small scale PTC occurs. Finally, within the framework of industrial turbulence simulations a fully kinetic Large Eddy Simulation formalism is derived based on the AG model. This strategy of directly applying the filter on the kinetic level is helpful to devise realizability conditions. Preliminary results for the AG-LES model are evaluated in 2D, in order to investigate the sensitivity of the LES result on the subgrid closures.