No description available.

The turbine is one of the key components in gas turbine engines. To prevent the turbine blades from being badly damaged by their harsh working environment, it is necessary to keep them cool. This can be achieved by enhancement of the heat transfer performance through internal cooling passages. However, the large quantity of flow within this internal cycle inevitably results in mass flow loss, which is a major source of loss in turbomachinery. Therefore labyrinth seals are also investigated in this study, attempting to reduce the flow leakage and further increase the turbine efficiency. Large Eddy Simulation ( LES ) is used for its capability to capture the complex unsteady flow features in this study. Different rib shapes in a fully developed ribbed channel are investigated, aiming to improve the heat transfer performance. An immersed boundary method ( IBM ) is used with LES to generate complex geometries. With the use of IBM , the range of geometries can be represented on a background Cartesian grid. To obtain the best sealing performance, an investigation is undertaken into the possibility of optimising labyrinth seal planforms using a genetic algorithm ( GA ). By making use of the large number of populations, a much faster calculation can be achieved toward the objective function. Three hundred LES calculations are carried out, and an optimised design is generated that maximises the sealing effectiveness. The optimised design shows a leakage reduction of about 27.6% compared to the baseline geometry. The optimisation process employing a GA will be continued. It is expected that automated optimisation as presented will become increasingly important in the design process of future turbomachines, particularly for flows with strong parameter interactions, with an aim to further improve the overall efficiency of gas turbines.

Written in French, this thesis presents a comparative and intertextual study on the theme of « windows » in four poems by Charles Baudelaire, Stéphane Mallarmé, Marie Krysinska and Guillaume Apollinaire. Charles Baudelaire (1821-1867), Stéphane Mallarmé (1842 -1898), Marie Krysinska (1857-1908) and Guillaume Apollinaire (1880-1918) use « windows » as a common theme in their poetry. My study compares this common theme found in four poems: (1) “Les fenêtres” by Charles Baudelaire in Spleen de Paris XXXV, 1869. (2) “Les fenêtres” by Stéphane Mallarmé in Le Parnasse Contemporain, 1863/66. (3) “Les fenêtres” by Marie Krysinska in Rythmes pittoresques, 1890. (4) “Les fenêtres” by Guillaume Apollinaire in Calligrammes (1913-1916), 1918. I focus on what distinguishes these fours poems by following the evolution of poetical forms between symbolism and futurism/surrealism. The common theme (“windows”) provides an opportunity to better underline the formal heterogeneity which separates these different “poetical avenues”: with Baudelaire, the newness of prose poetry; with Mallarmé, the symbolist renewal of a more classic form; with Apollinaire, a form of simultaneity inspired by futurism. The comparative analysis brings to light the original value of the poem written by Krysinska, whose works have not greatly captivated the attention of critics.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Dissertation--Universität Stuttgart. / Résumé en anglais p. 14-15. Bibliogr. p. 226-235.

Doctoral thesis--Göteborg, 1999. / Bibliogr. p. 217-218.

Thèse de doctorat : Sciences de l'Education : Paris 10 : 2009. / Thèse consultable uniquement dans l'enceinte de l'université Paris Ouest Nanterre La défense. Titre provenant de l'écran-titre.

Thèse (M.Sc.)--Université Laval, 2007. / Titre de l'écran-titre (visionné le 5 mai 2008). Bibliogr.

Diss.--Theologische Fakultät--Göttingen--Georg-August-Universität, 1997.

Thermal stripping is a major safety challenge in nuclear power generation and propulsion systems. It arises as a consequence of the heat transfer from fluid to surrounding solid components varying in time and typically occurs in regions where the mixing of hot and cold fluids results in turbulent temperature fluctuations. It can occur in a range of components in reactors and thermal-hydraulics systems and may lead to structural failure by high-cycle thermal fatigue. Cases of cooling system pipes failing by this mechanism have been reported at the French Civaux and the Japanese Tsuruga-2 & Tomari-2 pressurised water reactor plants. CFD has great potential to provide predictions for flow fields in the pipe bends and junctions of nuclear plant thermal-hydraulics systems. The current project aims to use CFD to explore the physics of thermal mixing in plant components, and to develop \& validate CFD techniques for studying such problems in industry. Firstly, wall-resolved LES is used to demonstrate the importance of including nearby upstream pipe bends in CFD studies of thermal mixing in T-junctions. Swirl-switching of the Dean vortices generated at an upstream bend can give rise to an unsteady secondary flow about the pipe axis. This provides an additional mechanism for low-frequency near-wall temperature fluctuations downstream of the T-junction, over those that would be produced by mixing in the same T-junction with straight inlets. Wall-resolved LES is however currently computationally unaffordable for studying plant components in industry. Wall-functions offer a solution to this problem by imposing empirical results near walls, such that a coarser grid can be used. LES with blended wall-function predictions for flows in a 90 degree pipe bend and a simple T-junction with straight inlets are compared to experimental data. These studies highlight limitations in the predictive capabilities of the LES with wall-function approach. Predictions from a number of RANS models are also benchmarked. Finally, the consistent dual-mesh hybrid LES/RANS framework proposed by Xiao and Jenny (2012) is further developed as an alternative solution to the high computational cost of wall-resolved LES. Numerous modifications to the coupling between the two meshes are presented, which improve automation and accuracy. The approach is also extended to a passive temperature scalar field. Predictions for channel flows, a flow through periodic hills and thermal mixing in a T-junction between channel flows are all in excellent agreement with reference data.