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Approches Theoriques Du Probleme Du Rayonnement Acoustique Par Une Entree Dair De Turboreacteur
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Book Synopsis Approches théoriques du problème du rayonnement acoustique par une entrée d'air de turboréacteur by : Stéphane Lidoine
Download or read book Approches théoriques du problème du rayonnement acoustique par une entrée d'air de turboréacteur written by Stéphane Lidoine and published by . This book was released on 2002 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'utilisation des méthodes numériques est désormais requise pour évaluer les performances acoustiques des nouvelles technologies envisagées pour améliorer la réduction du bruit rayonné par les entrées d'air de turboréacteur. Notre travail consiste à comparer les résultats en champ lointain fournis par quatre méthodes radicalement différentes et étudier l'origine des écarts observés. Par ailleurs, nous analysons séparément les différents phénomènes physiques intervenant dans le cadre de la propagation et du rayonnement acoustique au sein d'un écoulement potentiel, en présence de matériaux absorbants sur les parois du conduit. La méthode analytique, fondée sur la théorie modale et la technique de Wiener-Hopf est considérée ici comme la référence. Nous mettons en évidence des domaines de validité fréquentiels pour chacune des méthodes et insistons sur leur complémentarité. À basse fréquence, les méthodes numériques intégrales et FEM donnent les mêmes résultats en absence d'écoulement. Les principaux écarts par rapport aux résultats de la méthode analytique sont dus à la différence de forme de la lèvre considéré dans chaque méthode, arrondie ou à bords vifs. Le bon accord entre les résultats numériques et des résultats de mesures dans des configurations traitées complexes est essentiel pour compléter la validation et montrer l'intérêt de ces méthodes. Nous introduisons le concept d'écoulement quasi uniforme dans la méthode intégrale pour tenir compte des conditions aux limites sur les parois : les comparaisons avec les résultats analytiques montrent le bien-fondé de cette approximation. À haute fréquence, il est nécessaire d'utiliser une méthode asymptotique. La méthode choisie est basée sur la sommation des faisceaux gaussiens et se révèle pertinente pour effectuer des calculs multimodaux sur une plage angulaire dépendant de la fréquence et de la présence ou non de matériaux absorbants. Les différences observées sur le rayonnement des modes sont essentiellement dues à l'absence de prise en compte de la diffraction dans la solution asymptotique. Enfin, les études effectuées dans le cas d'un écoulement non uniforme et potentiel montrent que le paramètre aérodynamique fondamental est la valeur de la vitesse de l'écoulement à la source. De plus, les effets de réfraction au voisinage de la lèvre modifient le rayonnement de manière plus importante que les effets de convection par l'écoulement extérieur. La prise en compte d'un écoulement plus réaliste dans le modèle est abordée à la fin du mémoire en vue d'effectuer des comparaisons avec des mesures en soufflerie ou au banc statique.
Book Synopsis MODELISATION DE LA PROPAGATION ET DU RAYONNEMENT ACOUSTIQUES DES ENTREES D'AIR DE TURBOREACTEURS by : FABIENNE.. MONTETAGAUD
Download or read book MODELISATION DE LA PROPAGATION ET DU RAYONNEMENT ACOUSTIQUES DES ENTREES D'AIR DE TURBOREACTEURS written by FABIENNE.. MONTETAGAUD and published by . This book was released on 1998 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: DEVANT LA GENE CROISSANTE AUTOUR DES AEROPORTS, GENEREE PAR L'AUGMENTATION CONSTANTE DU TRAFIC AERIEN, LES CONSTRUCTEURS D'AVIONS SONT AMENES A TRAVAILLER, DES LA PHASE D'AVANT PROJET, A LA REDUCTION DU BRUIT A LA SOURCE, NOTAMMENT PAR TRAITEMENT ACOUSTIQUE DES NACELLES DE TURBOREACTEURS. POUR CELA, IL EST NECESSAIRE DE DISPOSER D'OUTILS DE CALCUL PERFORMANTS CAPABLES D'ESTIMER L'EFFICACITE DES REVETEMENTS ABSORBANTS PLACES SUR LES PAROIS INTERNES. C'EST PRECISEMENT DANS CE CONTEXTE QUE SE SITUE CETTE ETUDE, QUI PRESENTE ET ANALYSE DEUX METHODES COMPLEMENTAIRES PERMETTANT LA MODELISATION DE LA PROPAGATION ET DU RAYONNEMENT ACOUSTIQUES DES ENTREES D'AIR DE TURBOREACTEURS. LA PREMIERE EST UN MODELE ANALYTIQUE UTILISANT UNE DESCRIPTION MODALE DE LA PRESSION ACOUSTIQUE DANS UN CONDUIT CYLINDRIQUE INFINI DE SECTION CONSTANTE, AVEC OU SANS TRAITEMENT, ET PARCOURU PAR UN ECOULEMENT D'AIR. LA SECONDE PREND LE RELAIS A L'EXTREMITE DU CONDUIT POUR CALCULER LE RAYONNEMENT VERS L'EXTERIEUR AU MOYEN D'UNE REPRESENTATION PAR EQUATIONS INTEGRALES. L'ANALYSE APPROFONDIE DE CES DEUX METHODES, MENEE DANS LE CADRE DE LEUR APPLICATION A L'INSONORISATION DES NACELLES, MET EN EVIDENCE LEURS LIMITATIONS, LES CONSEQUENCES D'HYPOTHESES RESTRICTIVES, ET PROPOSE DES SOLUTIONS POUR PALLIER AU CARACTERE PARFOIS INSTABLE OU IMPRECIS DES METHODES DE RESOLUTION. PAR AILLEURS, UN COMPORTEMENT MODAL SINGULIER, LORS DU PASSAGE DU CONDUIT RIGIDE AU CONDUIT TRAITE, EST MIS EN EVIDENCE. ENFIN, LE COUPLAGE ENTRE LES DEUX CODES EST DEVELOPPE POUR PRENDRE EN COMPTE LA RUPTURE D'IMPEDANCE EN BOUT DE CONDUIT. LA VALIDATION EXPERIMENTALE MONTRE D'UNE PART L'INFLUENCE DU DEPHASAGE ENTRE LES MODES ET D'AUTRE PART UNE BONNE CORRELATION ENTRE LA MESURE ET LA MODELISATION QUAND UNE HYPOTHESE SUR LES DEPHASAGES EST ACCEPTABLE.
Book Synopsis Recent Findings on the Impairment of Airmanship by Alcohol by : Stanley R. Mohler
Download or read book Recent Findings on the Impairment of Airmanship by Alcohol written by Stanley R. Mohler and published by . This book was released on 1966 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamentals of Acoustics by : Michel Bruneau
Download or read book Fundamentals of Acoustics written by Michel Bruneau and published by John Wiley & Sons. This book was released on 2013-03-01 with total page 429 pages. Available in PDF, EPUB and Kindle. Book excerpt: The central theme of the chapters is acoustic propagation in fluid media, dissipative or non-dissipative, homogeneous or nonhomogeneous, infinite or limited, placing particular emphasis on the theoretical formulation of the problems considered.
Book Synopsis Large-Eddy Simulation for Acoustics by : Claus Wagner
Download or read book Large-Eddy Simulation for Acoustics written by Claus Wagner and published by Cambridge University Press. This book was released on 2007-01-15 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: Noise around airports, trains, and industries attracts environmental concern and regulation. Large-eddy simulation (LES) is used for noise-reduced design and acoustical research. This 2007 book, by 30 experts, presents the theoretical background of acoustics and LES, and details about numerical methods, e.g. discretization schemes, boundary conditions, and coupling aspects.
Download or read book Acoustics written by Allan D. Pierce and published by Springer. This book was released on 2019-06-22 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt: This corrected version of the landmark 1981 textbook introduces the physical principles and theoretical basis of acoustics with deep mathematical rigor, concentrating on concepts and points of view that have proven useful in applications such as noise control, underwater sound, architectural acoustics, audio engineering, nondestructive testing, remote sensing, and medical ultrasonics. Since its publication, this text has been used as part of numerous acoustics-related courses across the world, and continues to be used widely today. During its writing, the book was fine-tuned according to insights gleaned from a broad range of classroom settings. Its careful design supports students in their pursuit of a firm foundation while allowing flexibility in course structure. The book can easily be used in single-term or full-year graduate courses and includes problems and answers. This rigorous and essential text is a must-have for any practicing or aspiring acoustician.
Author :United States. National Aeronautics and Space Administration. Scientific and Technical Information Division Publisher : ISBN 13 : Total Pages :338 pages Book Rating :4.F/5 ( download)
Book Synopsis Dictionary of Technical Terms for Aerospace Use by : United States. National Aeronautics and Space Administration. Scientific and Technical Information Division
Download or read book Dictionary of Technical Terms for Aerospace Use written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Division and published by . This book was released on 1965 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: Brief definitions "intended to be as clear as possible to the non-expert, but accuracy has not been compromised for the sake of readability. Mathematics has been used where necessary to avoid ambiguity."--Intro. Published 1965.
Book Synopsis Uncertainty Quantification by : Christian Soize
Download or read book Uncertainty Quantification written by Christian Soize and published by Springer. This book was released on 2017-04-24 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the fundamental notions and advanced mathematical tools in the stochastic modeling of uncertainties and their quantification for large-scale computational models in sciences and engineering. In particular, it focuses in parametric uncertainties, and non-parametric uncertainties with applications from the structural dynamics and vibroacoustics of complex mechanical systems, from micromechanics and multiscale mechanics of heterogeneous materials. Resulting from a course developed by the author, the book begins with a description of the fundamental mathematical tools of probability and statistics that are directly useful for uncertainty quantification. It proceeds with a well carried out description of some basic and advanced methods for constructing stochastic models of uncertainties, paying particular attention to the problem of calibrating and identifying a stochastic model of uncertainty when experimental data is available. This book is intended to be a graduate-level textbook for students as well as professionals interested in the theory, computation, and applications of risk and prediction in science and engineering fields.
Book Synopsis Advanced Computational Vibroacoustics by : Roger Ohayon
Download or read book Advanced Computational Vibroacoustics written by Roger Ohayon and published by . This book was released on 2014 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents an advanced computational method for the prediction of sound and structural vibrations in several industries.
Book Synopsis Numerical Computation of Internal and External Flows, Volume 1 by : Charles Hirsch
Download or read book Numerical Computation of Internal and External Flows, Volume 1 written by Charles Hirsch and published by Wiley. This book was released on 1991-01-08 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical Computation of Internal and External Flows Volume 1: Fundamentals of Numerical Discretization C. Hirsch, Vrije Universiteit Brussel, Brussels, Belgium This is the first of two volumes which together describe comprehensively the theory and practice of the numerical computation of internal and external flows. In this volume, the author explains the use of basic computational methods to solve problems in fluid dynamics, comparing these methods so that the reader can see which would be the most appropriate to use for a particular problem. The book is divided into four parts. In the first part, mathematical models are introduced. In the second part, the various numerical methods are described, while in the third and fourth parts the workings of these methods are investigated in some detail. Volume 2 will be concerned with the applications of numerical methods to flow problems, and together the two volumes will provide an excellent reference for practitioners and researchers working in computational fluid mechanics and dynamics.
Book Synopsis New Directions in Linear Acoustics and Vibration by : Matthew Wright
Download or read book New Directions in Linear Acoustics and Vibration written by Matthew Wright and published by Cambridge University Press. This book was released on 2010-07-26 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of acoustics is of immense industrial and scientific importance. The subject is built on the foundations of linear acoustics, which is widely regarded as so mature that it is fully encapsulated in the physics texts of the 1950s. This view was changed by developments in physics such as the study of quantum chaos. Developments in physics throughout the last four decades, often equally applicable to both quantum and linear acoustic problems but overwhelmingly more often expressed in the language of the former, have explored this. There is a significant new amount of theory that can be used to address problems in linear acoustics and vibration, but only a small amount of reported work does so. This book is an attempt to bridge the gap between theoreticians and practitioners, as well as the gap between quantum and acoustic. Tutorial chapters provide introductions to each of the major aspects of the physical theory and are written using the appropriate terminology of the acoustical community. The book will act as a quick-start guide to the new methods while providing a wide-ranging introduction to the physical concepts.
Book Synopsis Immunology IV by : Joseph A. Bellanti
Download or read book Immunology IV written by Joseph A. Bellanti and published by . This book was released on 2012 with total page 1063 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bellanti's IMMUNOLOGY IV is a new, contemporary approach to teaching immunology that uses the most advanced pedagogical and online aids. Consisting of a full-color, heavily illustrated textbook plus an online service with animations, illustrations, interactive study questions and critical thinking aids, this is the perfect solution not only for faculty seeking to fully present this complex scientific discipline to students while focusing on its relation to real world clinical problem-solving but also for members of the medical professions. It is the ideal reference for residents and practitioners preparing for certification and board examinations. The structure, content and pedagogy allow users to retain more knowledge in less time than with traditional methods. Immunology has seen extraordinary developments in both scope and complexity during the last 40 years. World-renowned author, researcher and educator Joseph A. Bellanti, MD, has synthesized the most current research findings with clinical applications through an innovative new approach to teaching. This text and online service presents a unified approach by integrating principles with case studies to teach clinical realities. Each new book purchased includes a password for a two year individual subscription to the online service at www.immunologycenter.org. In the Preface of the book, Dr. Bellanti explains: "What was once a discipline defined in descriptive terms is now becoming better understood at the genomic and molecular levels." Because of this and the rapid development of treatment options, it is critical for students, residents and practitioners to fully understand the clinical implications of immunologic principles and mechanisms.
