Thèse de doctorat : Mécanique et Energétique : Nancy 1 : 2008. / Titre provenant de l'écran-titre.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnologico / Made available in DSpace on 2016-01-08T21:41:28Z (GMT). No. of bitstreams: 1 108926.pdf: 2175119 bytes, checksum: 7afd6e31b8175d67956389df8eb7456e (MD5) Previous issue date: 1997 / Nesta dissertação descreve-se a discretização das equações de Navier-Stokes e a resolução é feita através do uso de malhas não-estruturadas geradas por diagramas de Voronoi, em problemas envolvendo escoamentos de fluídos. São testados alguns gradientes de pressão disponíveis na literatura quanto a seu desempenho, como também sugere-se uma nova forma de avaliar tal gradiente de pressão.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnologico / Made available in DSpace on 2016-01-08T21:47:21Z (GMT). No. of bitstreams: 1 108177.pdf: 2040537 bytes, checksum: f1ed4f651ba64a96c7769a93e8b25a2b (MD5) Previous issue date: 1997 / Este trabalho apresenta uma metodologia em Volumes Finitos para a solução de problemas envolvendo escoamentos em corpos de águas rasas. Foram usados dois esquemas de interpolação, WUDS para os problemas unidimensionais e QUICK para os bidimensionais, mas nenhuma comparação é feita entre eles. O procedimento usado baseou-se no algoritmo para qualquer velocidade ("All-Speed"), usado na solução de escoamentos compressíveis, que consiste basicamente numa linearização da equação da conservação da massa para que se possa considerar simultaneamente os efeitos da pressão sobre a densidade e campo de velocidades. Os resultados comprovam a eficiência da proposta na reprodução de vários escoamentos usados como teste (unidimensionais e bidimensionais, permanentes e transientes). Também fica evidente a necessidade de tratar com mais cuidado as condições de contorno, especialmente nos escoamentos onde o tráfego de ondas é livre em qualquer direção e sentido.

The problem of surface area and particle size determination has been examined. A survey of the methods for measuring the surface areas and average sizes of aggregates of fine particles was made and a method selected for Improvement. An apparatus employing the principles of fine particle measurement established in turbidimetry was constructed. Experimental work with the apparatus was conducted in an attempt to establish a single method of particle size measurement. The results warrant the conclusion that the apparatus will measure average surface diameters of single component materials, constant assaying materials, and mixtures containing one semi-transparent material. A value for the relative surface area of these materials can also be determined. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

This thesis is an investigation of the separation of the public and private parts of a house, using stairs, walls and dropped ceilings to separate different spaces. The use of stairs to separate space creates rooms of different volumes. A further investigation of the transition between outdoors and indoors lead to the study of form through sketching. The site is located in a residential area in McLean, Virginia. It is a relatively flat site as there are no major slopes. The three acre lot is generous in size and was not meant to drive the design of the house by providing limits. Trees on three sides of the site provide a natural barrier between the adjacent lots, providing some privacy. The site is zoned such that it could have two driveways, one being used mostly by guests and the other by the occupants. / Master of Architecture

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La caractérisation 2D/3D et l’analyse d'images ont permis d’estimer les changements microstructuraux liés à : différents taux de Fe, Mn et Sr, au procédé de moulage (Coulée coquille par Gravité vs. Procédé à Modèle Perdu, PMP) et au traitement thermique de mise en solution d’un alliage A319. L'évolution de la microstructure avec les éléments d'addition a aussi été étudiée par analyse thermique. La microstructure est constituée d'inclusions dures (Si eutectique, intermétalliques au Fe et phases Al2Cu) et de pores. L'effet sur les propriétés mécaniques a été évalué par dureté Vickers et essais de traction. L’observation de l’endommagement en surface d’alliages A319 avec différentes teneurs en Fe est effectuée in situ au cours de l'essai de traction afin de suivre l'évolution et la localisation de la déformation et des fissures. La corrélation d’images numériques et la fractographie ont mis en évidence le rôle des intermétalliques au Fe dans l'amorçage et la propagation des fissures. Des essais de traction sur des échantillons A319 PMP avec deux conditions de traitement thermique ont été effectués in situ sous tomographie de laboratoire. Les mesures de déformation par corrélation de volumes numériques et les mécanismes d'endommagement observés montrent que les fissures s’amorcent aux inclusions dures dans les zones de concentration de contraintes, surtout autour des pores, et se propagent souvent par la rupture des phases Al2Cu, des intermétalliques au Fe, et du Si eutectique, plutôt que par leur décohésion de la matrice. / 2D and 3D characterization and image analysis have been performed to measure the microstructural changes associated with: different Sr, Fe and Mn levels, the casting process (Gravity Die Casting vs. Lost Foam Casting, LFC) and the solution heat treatments in A319 alloy. The evolution of microstructure in Al-Si-Cu alloy with different alloying elements addition was also studied by thermal analysis. The microstructure consists of hard inclusions, i.e. eutectic Si, iron-intermetallics and Al2Cu phases, and pores. The effect on mechanical properties of the alloys has been monitored by Vickers hardness measurement and tensile tests. Surface damage observations are performed on A319 alloys with different Fe content during in-situ tensile test, which allows following the development and localization of the deformation and cracks. Digital image correlation measurement and fractography highlighted the role of iron-intermetallics in the cracks initiation and propagation. Tensile tests on LFC A319 samples with two different heat treatment conditions were performed in-situ under Laboratory Computed Tomography. Strain measurements from digital volume correlation and observed damage mechanisms show that cracks initiate at hard inclusions in the areas with sufficient stress concentrations, which are mainly provided by large pores, and often propagate through the fracture of Al2Cu, iron-intermetallics, as well as through Si particles rather than by their decohesion from the matrix.

Dans ce travail, nous proposons différentes méthodes de Volumes Finis (centrée cellule, Éléments-Volumes Finis conforme et Éléments-Volumes Finis non conforme) pour des problèmes où surviennent des singularités. Nous nous intéressons tout d'abord au cas des singularités de coin intervenant en dimension deux pour diverses problèmes elliptiques (problème de Laplace, systèmes de Stokes et de Navier-Stokes). En effet, lorsque nous considérons un problème elliptique sur un domaine non convexe de R², la présence de singularités de coin détériore l'ordre de convergence des méthodes numériques (Différences Finies, Éléments Finis ou Volumes Finis). Nous montrons alors comment, pour les diverses méthodes de Volumes Finis étudiées, un raffinement de maillage local permet de restaurer un ordre de convergence optimal. Nous abordons ensuite les problèmes de couche limite en dimension deux intervenant dans les problèmes singulièrement perturbés. La solution de tels problèmes est caractérisée par un fort gradient local que n'arrive pas à capturer les méthodes de Volumes Finis sur des maillages standards. Nous étudions donc, pour un problème modèle de réaction-diffusion perturbé, la convergence des méthodes de Volumes Finis centrée cellule, d'Éléments- volumes Finis conforme et d'Éléments- volumes Finis non conformes sur des maillages anisotropes. Nous évoquons en dernier lieu le cas des singularités intervenant en dimension trois. Pour le cas du problème de Laplace considéré sur un domaine non convexe tridimensionnel et discrétisé par les méthodes de Volumes précédemment vues, nous illustrons numériquement, d'une part, le fait que les maillages uniformes apportent un ordre de convergence non optimal, et d'autre part, comment un raffinement de maillage local permet d'améliorer la situation.

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