This thesis is concerned with the new formulation of a finite-volume lattice Boltzmann equation method and its implementation on unstructured meshes. The finite-volume discretization with a cell-centered tessellation is employed. The new formulation effectively adopts a total variation diminishing concept. The formulation is analyzed for the modified partial differential equation and the apparent viscosity of the model. Further, the high-order extension of the present formulation is laid out. Parallel simulations of a variety of two-dimensional benchmark flows are carried out to validate the formulation. In Chapter 1, the important notions of the kinetic theory and the most celebrated equation in the kinetic theory, ‘the Boltzmann equation’ are given. The historical developments and the theory of a discrete form of Boltzmann equation are briefly discussed. Various off-lattice schemes are introduced. Various methodologies adopted in the past for the solution of the lattice Boltzmann equation on finite-volume discretization are reviewed. The basic objectives of this thesis are stated. In Chapter2,the basic formulations of lattice Boltzmann equation method with a rational behind different boundary condition implementations are discussed. The benchmark flows are studied for various flow phenomenon with the parallel code developed in-house. In particular, the new benchmark solution is given for the flow induced inside a rectangular, deep cavity. In Chapter 3, the need for off-lattice schemes and a general introduction to the finite-volume approach and unstructured mesh technology are given. A new mathematical formulation of the off-lattice finite-volume lattice Boltzmann equation procedure on a cell-centered, arbitrary triangular tessellation is laid out. This formulation employs the total variation diminishing procedure to treat the advection terms. The implementation of the boundary condition is given with an outline of the numerical implementation. The Chapman-Enskog (CE) expansion is performed to derive the conservation equations and an expression for the apparent viscosity from the finite-volume lattice Boltzmann equation formulation in Chapter 4. Further, the numerical investigations are performed to analyze the apparent viscosity variation with respect to the grid resolution. In Chapter 5, an extensive validation of the newly formulated finite-volume scheme is presented. The benchmark flows considered are of increasing complexity and are namely (1) Posieuille flow, (2) unsteady Couette flow, (3) lid-driven cavity flow, (4) flow past a backward step and (5) steady flow past a circular cylinder. Further, a sensitivity study to the various limiter functions has also been carried out. The main objective of Chapter6is to enhance the order of accuracy of spatio-temporal calculations in the newly presented finite-volume lattice Boltzmann equation formulation. Further, efficient implementation of the formulation for parallel processing is carried out. An appropriate decomposition of the computational domain is performed using a graph partitioning tool. The order-of-accuracy has been verified by simulating a flow past a curved surface. The extended formulation is employed to study more complex unsteady flows past circular cylinders. In Chapter 7, the main conclusions of this thesis are summarized. Possible issues to be examined for further improvements in the formulation are identified. Further, the potential applications of the present formulation are discussed.

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Serial Editions: Another Book of Books for the Chapman is a collection of chapbooks whose titles include First Cold Morning, River Music, Vow, Intimate Interactions of a Corollary ( w/ braille translations), My Soul From Yesterday & Another Abecedarian for the World. You may or might not get a postcard in the mail announcing its distribution, then, one chapbook at a time, as in serial comics, slowly collecting, only later to receive them all, collected in a single book object..

The task of this diploma thesis is the Lattice Boltzmann method (LBM). LBM is a mesoscopic method describing the particle motion in a fluid by the Boltzmann equation, where the distribution function is involved. The Chapman-Enskog expansion shows the connection with the macroscopic Navier-Stokes equations of conservation laws. In this process the Hermite polynoms are used. The Lattice Boltzmann equation is derived by the discretisation of velocity, space and time which is concluding to the numerical algorithm. This algorithm is applied at two problems of fluid flow: the two-dimensional square cavity and a flow arround obstacles. In both cases were the results of velocities compared to results calculated by finite volume method (FVM). The relative errors are in order of multiple 1 %.

Les lacs de thermokarst sont principalement répartis dans les régions de pergélisol. Leur formation et développement sont principalement associés au dégel du pergélisol riche en glace ou à la fonte des coins de glace. Ces lacs peuvent s'assécher complètement ou partiellement par le biais de divers processus, tels que le débordement des berges, la formation de voies de drainage, la capture par les méandres des rivières. Le drainage des lacs de thermokarst est un aléa important lié au pergélisol. Malgré de nombreuses études portant sur les événements historiques de drainage des lacs de thermokarst, les études explorant le potentiel de drainage futur des lacs de thermokarst sont limitées. Ce mémoire présente une étude de cas menée sur le complexe morainique du lac Chapman, situé à km 116 de l’autoroute Dempster, dans le centre du Yukon, au Canada. De multiples perturbations du pergélisol signalées dans cette région indiquent que le pergélisol est en dégradation. Le lac Chapman, un grand lac de thermokarst d’origine glaciaire situé à environ 50 m du remblai de l’autoroute de Dempster, est choisi pour étudier son potentiel de drainage. Cette recherche a utilisé diverses approches et appliqué de multiples analyses, notamment le modèle numérique d'élévation, la bathymétrie du lac, la cryostratigraphie du pergélisol, la cristallographie de la glace, la tomographie de résistivité électrique et l'hydrochimie. Cette recherche vise à interpréter les conditions locales de pergélisol et de glace souterraine dans lesquelles le drainage lacustre pourrait se produire, ainsi qu'à élucider les mécanismes de drainage potentiels associés au paysage local, à la topographie, à la géomorphologie, aux propriétés du sol et aux conditions hydrologiques. Cette recherche révèle que le lac Chapman a tendance à se drainer partiellement par le biais de deux mécanismes possibles : la migration du chenal de la rivière Blackstone et la formation de chenaux de drainage de ravins. Ce drainage potentiel pourrait entraîner une érosion thermique sur l'environnement adjacent de pergélisol, en particulier sur le remblai de l’autoroute Dempster. / Thermokarst lakes are predominantly distributed across permafrost-affected areas. Their formation and development are primarily associated with thawing of ice-rich permafrost or melting of ice wedges. These lakes can drain completely or partially through various processes, such as bank overtopping, the formation of drainage pathways, or capture by river meandering. The drainage of thermokarst lake is an important permafrost-related geohazard. Despite numerous studies focusing on historical thermokarst lake drainage events, the studies exploring the future potential drainage of thermokarst lakes are limited. This thesis presents a case study conducted at the Chapman Lake moraine complex, located at km 116 of the Dempster Highway in central Yukon, Canada. Multiple permafrost disturbances reported in this region indicate that permafrost degradation is ongoing. Chapman Lake, a large glacial-thermokarst lake situated approximately 50 m from the road embankment of Dempster Highway, is selected to investigate its potential drainage. This research used various methods and applied multiple analyses including digital elevation model, lake bathymetry, permafrost cryostratigraphy, ice crystallography, electrical resistivity tomography, and hydrochemistry. This research aims to interpret the local permafrost and ground ice settings where lake drainage may occur and to elucidate the potential drainage mechanisms associated with the local landscape, topography, geomorphology, soil properties and hydrologic conditions. This research reveals that Chapman Lake tends to partially drain through two possible mechanisms: river channel migration of the Blackstone River and the formation of gully drainage channels. This potential drainage could lead to thermal erosion in adjacent permafrost environment, particularly in relation to the Dempster Highway.

La miniaturisation de plus en plus poussée (micro et nano) des systèmes mécanique connaît un important développement depuis une dizaine d'années. Leur conception et réalisation nécessite une connaissance approfondie des écoulements micro-fluidiques. Dans le domaine énergétique, le rendement d'un moteur thermique se dégrade sérieusement lors d'une réduction d'échelle. En effet, les pertes de chaleur pariétales peuvent devenir aussi importantes que l'énergie libérée. Une voie prometteuse consiste à utiliser les ondes de choc / détonation pour accélérer la libération d'énergie. Dans ce cas, la détonation peut être assimilée à une onde de choc inerte, couplée à une zone de réaction, caractérisée par la présence d'instabilités longitudinales et transverses, soumettant ainsi le front de choc à de violentes accélérations / décélérations. L'objectif de la thèse est de mieux appréhender la structure moyenne de la zone de réaction qui s'étend du choc jusqu'à la surface sonique. Sur le plan de la modélisation numérique, les équations de Navier-Stokes compressibles, multi-espèces, réactives sont résolues au sein du solveur CHOC-WAVES développé au CORIA, avec une thermodynamique variables et des coefficients de transport dépendant des espèces. La condition de Chapman-Jouguet généralisée a été élaborée et confirmée par les résultats de simulations numériques dans le cas d'une détonation multidimensionnelle stable. En particulier, il a été montré que les instabilités transverses s'atténuaient avec la réduction d'échelle. A cet effet, un scénario a été proposé pour expliquer le déficit de la vitesse du front de détonation, en se basant sur la structure de la poche subsonique aval, en corrélation avec l'épanouissement de la couche limite. Ce schéma partage de fortes similitudes avec la macro-détonation, tout en gardant des différences. En particulier, il a été montré que la forte vorticité, produite au niveau de la singularité de Prandtl-Meyer, souvent négligée dans les modèles de macro-détonation, diffusait au sein de la poche subsonique. Ces résultats tout à fait originaux ont permis une avancée significative dans la compréhension du mécanisme de propagation des fronts de détonation stables et confinées.

The main objective of this thesis is to study the fundamental behaviour of multi-component gas mixture flows in micro/nano-channels undergoing catalytic chemical reactions on the walls. This work is primarily focused on nano-scale reacting flows seen in related applications; especially, miniaturized energy sources such as micro-fuel cells and batteries. At these geometries, the order of the characteristic length is close to the mean free path of the flowing gas, making the flow highly rarefied. As a result, non-equilibrium conditions prevail even the bulk flow and therefore, continuum assumptions are not held anymore. Hence, discrete methods should be adopted to simulate molecular movements and interactions described by the Boltzmann equation. The Direct Simulation Monte Carlo (DSMC) method was employed for the present research due to its natural ability for simulating a broad range of rarefied gas flows, and its flexibility to incorporate surface chemical reactions. In the first step, fluid dynamics and the heat transfer of H₂/N₂ and H₂/N₂/CO₂ gas mixture slip flows in a plain micro-channel are simulated. The obtained results are compared to the corresponding data achieved from Navier-Stokes equations with slip/jump boundary conditions. Generally, very good agreements are observed between the two methods. It proves the ability of DSMC in replicating the fluid properties of multi-component gas mixtures even when high mass discrepancies exist among the species. Based on this comparison, the proper parameters are set for the prepared DSMC code, and the appropriate intermolecular collision model is identified. It is also found that stream variables should be calculated more accurately at flow boundaries in order to simulate the intense upstream diffusion emerging at low velocity flows frequently seen in micro/nano-applications. Therefore, in the second step, a novel pressure boundary condition is introduced for gas mixture flows by substituting the commonly used Maxwell velocity distribution with the Chapman-Enskog distribution function. It is shown that this new method yields better results for lower velocity and higher rarefaction level cases. In the last step, a new method is proposed for coupling the flow field simulated by DSMC and surface reactions modelled by the species conservation ODE system derived from the reaction mechanism. First, a lean H₂/air slip flow subjected to oxidation on platinum coated walls in a flat micro-channel 4μm in height is simulated as a verification test case. The results obtained are validated against the solutions of the Navier-Stokes equations with slip/jump boundary conditions and very good conformity is achieved. Next, several cases undergoing the same reaction with Reynolds numbers ranging from 0.2 to 3.6 and Knudsen numbers ranging from 0.025 to 0.375, are simulated using the verified code to investigate the effects of the channel height ranging from 0.5μm to 2μm , the inlet mass flow rate ranging from 5 kg/m².s to 25 kg/m².s, the inlet temperature ranging from 300K to 700K, the wall temperature ranging from 300K to 1000K, and the fuel/air equivalence ratio ranging from 0.28 to 1.5. Some of the findings are as follows: (1) increasing the surface temperature from 600K to 1000K and/or the inlet temperature from 300K to 700K results in negligible enhancement of the conversion rate, (2) the optimum value of the equivalence ratio is on the fuel lean side (around 0.5), (3) the efficiency of the reactor is higher for smaller channel heights, and (4) increasing the inlet mass flux elevates the reaction rate especially for the smaller channels; this effect is not linear and is more magnified for lower mass fluxes.

In this thesis I explore the global circulation and cross-cultural encounters of women advocacy travelers in the early twentieth century. I focus on Carrie Chapman Catt, Margaret Hodge, Mildred McFaden, and Madeleine Z. Doty, who journeyed around the world in order to advocate for women’s rights and peace. Catt traveled on behalf of the International Woman Suffrage Alliance (IWSA) to South Africa, the Middle East, and Asia in 1911-12, Hodge promoted women’s suffrage around the British dominions, and McFaden and other members of the American Woman’s Republic brought a resolution linking peace and women’s suffrage to the IWSA congress in Budapest in 1913. Doty made several journeys from the U.S. to Germany and Russia, as a dissident antiwar journalist during the First World War. Using their travel writings, I explore these women travelers, their encounters with women from other countries and cultures, and their ideas about internationalism and inclusion in the worldwide movement for women’s rights.

No Abstract Provided / Thesis / Candidate in Philosophy