Download or read book G n ration de m triques pour adaptation anisotrope de maillages applications la mise en forme des mat riaux written by Cyril Gruau and published by . This book was released on 2004 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Trois problèmes de construction de maillages sont devenus incontournables pour les logiciels de calcul scientifique : le traitement des géométries minces et courbées, la représentation multidomaine d'une simulation qui implique plusieurs objets et l'introduction de couches limites.Pour placer plusieurs couches d'éléments dans l'épaisseur des géométries minces et courbées, nous introduisons la notion de métrique naturelle qui, grâce à un processus d'adaptation anisotrope par optimisation topologique, permet de construire automatiquement un maillage convenable.Pour enrichir un maillage autour des interfaces entre les différents objets d'une simulation multidomaine, nous proposons une deuxième métrique qui permet de raffiner de manière anisotrope les éléments au voisinage de ces surfaces.Cette métrique multidomaine permet aussi la construction de couches limites. Enfin, deux autres voies pour améliorer la métrique naturelle sont explorées : l'anisotropie des champs calculés par une simulation et l'uniformisation d'un indicateur d'erreur a posteriori.
Download or read book Adaptation de Maillage Anisotrope written by Raphaël Kuate and published by Omniscriptum. This book was released on 2018-02-28 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'adaptation de maillage anisotrope consiste modifier un maillage de mani re non uniforme en espace et en direction. Son objectif principal est de trouver le maillage garantissant un meilleur crit re moindre co t pour optimiser les simulations num riques d' quations aux d riv es partielles. Cette th se est consacr e aux tudes th oriques et num riques de probl mes li s l'adaptation de maillage anisotrope: - Les m triques et estimateurs d'erreur qui permettent de sp cifier la taille locale des mailles. - Les modifications locales de maillages hexa driques conformes qui sont moins ais es qu'avec des triangulations, en raison de leur structure form e de couches. Tout d coupage trivial d'un hexa dre pouvant se propager jusqu' la fronti re. Nous mettons en oeuvre de nouveaux algorithmes et sch mas num riques pour la reconstruction de d riv es secondes et troisi mes, estimateurs d'erreur d'interpolation, ainsi que la construction de m triques, g n ralis e aux erreurs d'interpolation d'ordre sup rieur. Nous proposons de nouvelles op rations locales de raffinement/d -raffinement de maillages hexa driques conformes.
Download or read book Adaptation anisotrope pour maillages d l ments d ordre lev written by Arthur Bawin and published by . This book was released on 2018 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dans le cadre de la simulation par éléments finis, l'utilisation de maillages anisotropes permet d'atteindre des niveaux de précision souvent inégalés par ceux des maillages isotropes classiques, tout en diminuant considérablement le nombre de degrés de liberté du problème. Cette diminution de la taille du système linéaire entraîne des gains importants en termes de mémoire et de temps de calcul. En permettant l'étirement des éléments selon certaines directions privilégiées, les maillages adaptés s'ajustent aux caractéristiques du domaine de calcul et de la solution du problème différentiel. Si leur utilisation pour des éléments linéaires est maintenant répandue, l'adaptation anisotrope pour des maillages d'ordre élevé est encore rare, principalement à cause de la perte de lien entre l'erreur d'interpolation et l'écriture du tenseur métrique. Ce mémoire présente une méthodologie de calcul de champs de tenseurs métriques, utilisables pour la génération de maillages d'éléments anisotropes munis de fonctions d'interpolation d'ordre supérieur à un. Les maillages sont obtenus comme le minimisant de l'erreur d'interpolation sur le domaine de calcul. La littérature récente dans ce domaine traitant principalement d'adaptation sur des champs analytiques, on se propose d'appliquer cette méthodologie à des maillages d'éléments de Taylor-Hood pour la simulation d'écoulements simples en mécanique des fluides. En particulier, des maillages anisotropes sont présentés pour les problèmes de cavité entraînée et de marche descendante en deux dimensions. Le concept de maillage continu sert de passerelle entre le maillage discret, support du calcul par éléments finis, et les outils continus que sont l'optimisation et le calcul tensoriel. Cette représentation continue d'un maillage est étroitement liée au tenseur métrique, qui contient les informations d'anisotropie nécessaires pour mener l'adaptation. De ce tenseur, on peut extraire en chaque sommet les tailles, directions et étirement des éléments du maillages. Pour des éléments linéaires, la métrique était construite à partir de la matrice hessienne de la solution. L'analogie n'existe plus pour les éléments d'ordre supérieur, pour lesquels l'erreur d'interpolation inclut le tenseur des dérivées d'ordre plus élevé. La méthode explorée dans ce travail consiste à majorer localement cette expression tensorielle de l'erreur par une forme quadratique, puis d'en extraire la métrique associée. Ce faisant, on retrouve une correspondance entre le tenseur métrique et la mesure de l'erreur. On présente des maillages présentant un caractère anisotrope prononcé, pour des champs analytiques et des problèmes physiques. L'utilisation de fonctions présentant des gradients importants permet de tester les limites de la solution proposée. Finalement, on montre que les ordres de convergence en maillages obtenus concordent avec le taux fourni par la théorie sous-jacente à l'adaptation par métriques optimales.
Download or read book Adaptation de maillage anisotrope written by Éloïse Boiteau and published by . This book was released on 2012 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ce mémoire porte sur l'adaptation de maillage par métrique. Plus précisément, on s'intéresse à développer la métrique discutée dans l'article [10] de Pagnutti & Ollivier-Gooch puis à voir l'amélioration d'une telle méthode d'adaptation de maillage sur la résolution numérique d'une équation aux dérivées partielles par éléments finis. On présente d'abord l'intuition derrière l'adaptation de maillage par métrique, d'où on introduit une approximation de l'erreur d'interpolation. On parle de la convergence d'une solution numérique. Pour se mettre en situation de maillage par métrique classique et l'adaptation hiérachique. Puis, au vif du sujet, on explique l'approche de l'adaptation de maillage de Pagnutti & Ollivier-Gooch. On parle aussi des actions permettant d'adapter nos maillages. Enfin, on résout numériquement des équations aux dérivées partielles avec opérateur laplacien par la méthode des élments finis sur des maillages uniformes et adaptés par nos 3 méthodes d'adaptation. On y considère des cas 1D, 2D et 3D.
Download or read book Adaptation de maillage anisotrope en trois dimensions written by Frédéric Alauzet and published by . This book was released on 2003 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Theory of Propellers written by Theodore Theodorsen and published by . This book was released on 1944 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Summary: A technical method is given for calculating the axial interference velocity of a propeller. The method involves the use of certain weight functions P, Q, and F. Numerical values for the weight functions are given for two-blade, three-blade, and six-blade propellers.
Download or read book Satellite Situation Report written by Goddard Space Flight Center. Office of Public Affairs and published by . This book was released on 1977 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Reactor Physics written by Alain Hébert and published by Presses inter Polytechnique. This book was released on 2009 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geosimulation written by Itzhak Benenson and published by John Wiley & Sons. This book was released on 2004-08-20 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geosimulation is hailed as ‘the next big thing’ in geographic modelling for urban studies. This book presents readers with an overview of this new and innovative field by introducing the spatial modelling environment and describing the latest research and development using cellular automata and multi-agent systems. Extensive case studies and working code is available from an associated website which demonstrate the technicalities of geosimulation, and provide readers with the tools to carry out their own modelling and testing. The first book to treat urban geosimulation explicitly, integrating socio-economic and environmental modelling approaches Provides the reader with a sound theoretical base in the science of geosimulation as well as applied material on the construction of geosimulation models Cross-references to an author-maintained associated website with downloadable working code for readers to apply the models presented in the book Visit the Author's Website for further information on Geosimulation, Geographic Automata Systems and Geographic Automata Software http://www.geosimulationbook.com
Download or read book Transport Theory written by James J. Duderstadt and published by John Wiley & Sons. This book was released on 1979 with total page 630 pages. Available in PDF, EPUB and Kindle. Book excerpt: Problems after each chapter
Download or read book The Use of Analog and Digital Computers in Hydrology Proceedings of the Tucson Symposium written by tucson Symposium on the use of analog and digital computers in hydrology and published by . This book was released on 1969 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Computational Science written by Yousry Azmy and published by Springer Science & Business Media. This book was released on 2010-04-15 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear engineering has undergone extensive progress over the years. In the past century, colossal developments have been made and with specific reference to the mathematical theory and computational science underlying this discipline, advances in areas such as high-order discretization methods, Krylov Methods and Iteration Acceleration have steadily grown. Nuclear Computational Science: A Century in Review addresses these topics and many more; topics which hold special ties to the first half of the century, and topics focused around the unique combination of nuclear engineering, computational science and mathematical theory. Comprising eight chapters, Nuclear Computational Science: A Century in Review incorporates a number of carefully selected issues representing a variety of problems, providing the reader with a wealth of information in both a clear and concise manner. The comprehensive nature of the coverage and the stature of the contributing authors combine to make this a unique landmark publication. Targeting the medium to advanced level academic, this book will appeal to researchers and students with an interest in the progression of mathematical theory and its application to nuclear computational science.
Download or read book The Physics of Nuclear Reactors written by Serge Marguet and published by Springer. This book was released on 2018-02-26 with total page 1462 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive volume offers readers a progressive and highly detailed introduction to the complex behavior of neutrons in general, and in the context of nuclear power generation. A compendium and handbook for nuclear engineers, a source of teaching material for academic lecturers as well as a graduate text for advanced students and other non-experts wishing to enter this field, it is based on the author’s teaching and research experience and his recognized expertise in nuclear safety. After recapping a number of points in nuclear physics, placing the theoretical notions in their historical context, the book successively reveals the latest quantitative theories concerning: • The slowing-down of neutrons in matter • The charged particles and electromagnetic rays • The calculation scheme, especially the simplification hypothesis • The concept of criticality based on chain reactions • The theory of homogeneous and heterogeneous reactors • The problem of self-shielding • The theory of the nuclear reflector, a subject largely ignored in literature • The computational methods in transport and diffusion theories Complemented by more than 400 bibliographical references, some of which are commented and annotated, and augmented by an appendix on the history of reactor physics at EDF (Electricité De France), this book is the most comprehensive and up-to-date introduction to and reference resource in neutronics and reactor theory.
Download or read book Mechanical Vibration written by William John Palm and published by . This book was released on 2007 with total page 728 pages. Available in PDF, EPUB and Kindle. Book excerpt: Model, analyze, and solve vibration problems, using modern computer tools. Featuring clear explanations, worked examples, applications, and modern computer tools, William Palm's Mechanical Vibration provides a firm foundation in vibratory systems. You'll learn how to apply knowledge of mathematics and science to model and analyze systems ranging from a single degree of freedom to complex systems with two and more degrees of freedom. Separate MATLAB sections at the end of most chapters show how to use the most recent features of this standard engineering tool, in the context of solving vibration problems. The text introduces Simulink where solutions may be difficult to program in MATLAB, such as modeling Coulomb friction effects and simulating systems that contain non-linearities. Ample problems throughout the text provide opportunities to practice identifying, formulating, and solving vibration problems. KEY FEATURES Strong pedagogical approach, including chapter objectives and summaries Extensive worked examples illustrating applications Numerous realistic homework problems Up-to-date MATLAB coverage The first vibration textbook to cover Simulink Self-contained introduction to MATLAB in Appendix A Special section dealing with active vibration control in sports equipment Special sections devoted to obtaining parameter values from experimental data
Download or read book Transonic Aerodynamics written by L. Pamela Cook and published by SIAM. This book was released on 1993-01-01 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume offers exciting results, perspectives, and case studies for the treatment of problems arising in transonic aerodynamics. New advances including triple deck theory, analysis of stagnation at the nose of a body, transonic choked flow, and the transonic area rule are presented. Interest in analyzing the transonic range of flight, its stability properties, and especially the question of designing reduced drag (shockless or weak shock) airfoils keeps growing. Present day commercial aircraft cruise in the transonic range. Mechanical and aeronautical engineers interested in compressible fluid flows, design of optimal wings, and an understanding of transonic flow held about wings and airfoils will find the book invaluable. This book is understandable to those with a knowledge of continuum mechanics (fluids) and asymptotic methods. It is appropriate for graduate courses in aerodynamics and mathematical methods.
Download or read book Indicators of Environmental Quality written by William A. Thomas and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: Researchers and agencies collect reams of objective data and authors publish volumes of subjective prose in attempts to explain what is meant by environmental quality. Still, we have no universally recognized methods for combining our quantitative measures with our qualitative concepts of environ ment. Not all of our environmental goals should be reduced to mere numbers, but many of them can be; and without these quantitative terms, we have no way of defining our present position nor of selecting positions we wish to attain on any logically established scale of environmen tal values. Stated simply, in our zeal to measure our environment we often forget that masses of numbers describing a system are insufficient to understand it or to be used in selecting goals and priorities for expending our economic and human resources. Attempts at quantitatively describing environmental quality, rather than merely measuring different environmental variables, are relatively recent. This condensing of data into the optimum number of terms with maximum information content is a truly interdisciplinary challenge. When Oak Ridge National Laboratory initiated its Environmental Program in early 1970 under a grant from the National Science Foundation, the usefulness of environmental indicators in assessing the effects of technology was included as one of the initial areas for investigation. James L. Liverman, through his encouragement and firm belief that these indicators are indispensable if we are to resolve our complex environmental problems, deserves much of the credit for the publication of this book.
Download or read book Space Debris written by Heiner Klinkrad and published by Springer Science & Business Media. This book was released on 2006-09-01 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: The future evolution of the debris environment will be forecast on the basis of traffic models and possible hazard mitigation practices. The text shows how large trackable objects will have re-entry pinpointed and predictions made on related risk assessment for possible ground impact. Models will also be described for meteoroids which are also a prevailing risk.
