Download or read book tude num rique du bruit de jet rayonn par les structures coh rentes de la turbulence written by François Bastin and published by . This book was released on 1995 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: On propose une approche numérique originale de la prévision du bruit de jet, basée sur l'hypothèse que le rayonnement acoustique de l'écoulement est principalement dû à la contribution des structures cohérentes de la turbulence. On utilise pour cela un modèle de turbulence semi-déterministe qui permet d'obtenir les fluctuations cohérentes de l'écoulement tandis que les fluctuations aléatoires sont modélisées. Pour évaluer le bruit produit, on utilise ensuite l'analogie de Lighthill. La formulation choisie, exprimée dans l'espace de Fourier, est associée à une interprétation géométrique du processus de rayonnement dans le plan des nombres d'onde et des fréquences qui s'avère un outil puissant pour l'analyse des résultats acoustiques, présentés ici pour un jet plan subsonique et deux jets plans supersoniques

Download or read book Relation entre la structure a rodynamique d coulements turbulents incompressibles et le bruit mis cas du jet libre et d une cavit peu profonde written by Hervé Lazure and published by . This book was released on 1997 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: CETTE ETUDE DES BRUITS D'ORIGINE AERODYNAMIQUE GENERES PAR DES ECOULEMENTS TURBULENTS INCOMPRESSIBLES A POUR OBJECTIFS DE MIEUX COMPRENDRE LES MECANISMES DE PRODUCTION D'ENERGIE ACOUSTIQUE ET DE REDUIRE LES NUISANCES SONORES EN AGISSANT SUR LA STRUCTURE DE L'ECOULEMENT. UNE ETUDE NUMERIQUE DES MECANISMES DE PRODUCTION SONORE DE LA TURBULENCE EST APPLIQUEE AU CAS DU JET LIBRE. A PARTIR DE LA SIMULATION DU CHAMP AERODYNAMIQUE PAR UN MODELE K-, NOUS APPLIQUONS LE MODELE DE RIBNER QUI PERMET D'ESTIMER LES NIVEAUX DU RAYONNEMENT ACOUSTIQUE EN CHAMP LOINTAIN. APRES AVOIR VALIDE LA METHODE, NOUS ETUDIONS L'INFLUENCE DES PARAMETRES SECONDAIRES COMME L'INTENSITE DE TURBULENCE OU LA DIVERGENCE DU JET A LA SORTIE DE LA CONDUITE, A DEBIT ET DIAMETRE DE JET FIXES. EN PRATIQUE, CES DIFFERENTS PARAMETRES SONT MODIFIES PAR L'INTERMEDIAIRE DE LA CONFIGURATION GEOMETRIQUE DE LA BOUCHE DE SOUFFLAGE (FORME, GRILLES, DEFLECTEURS...). LES PRINCIPALES CONCLUSIONS DE CETTE ETUDE APPLIQUEE AUX CAS DES JETS SIMPLES, ANNULAIRES ET COAXIAUX MONTRENT QU'IL EST IMPORTANT DE RENDRE L'ECOULEMENT LE MOINS TURBULENT POSSIBLE A LA SORTIE DE LA CONDUITE ET QU'ELARGIR LE JET PEUT S'AVERER ETRE UN BON MOYEN DE REDUIRE LE BRUIT. LA SECONDE PARTIE DE CETTE ETUDE S'INTERESSE AU COMPORTEMENT AEROACOUSTIQUE DE LA CAVITE SOUS LES PANTOGRAPHES DU TGV. NOUS AVONS MIS EN PLACE UNE MAQUETTE DE LA CAVITE DANS UNE SOUFFLERIE ANECHOIQUE ET REALISE DES MESURES DE VITESSE PAR ANEMOMETRIE A FILS CHAUDS, DE FLUCTUATIONS DE PRESSION EN PAROI ET DU RAYONNEMENT ACOUSTIQUE EN CHAMP LOINTAIN. CETTE ETUDE EST COMPLETEE PAR DES SIMULATIONS NUMERIQUES DE L'ECOULEMENT A L'AIDE DU MODELE RNG K-. LE RAPPORT LONGUEUR SUR HAUTEUR DE LA CAVITE ETANT DE L'ORDRE DE HUIT, IL ETAIT TRES DIFFICILE DE PREVOIR LA STRUCTURE DE L'ECOULEMENT. LES VISUALISATIONS DE L'ECOULEMENT SUR LES PAROIS ET LES MESURES ANEMOMETRIQUES MONTRENT QUE L'ECOULEMENT SE RATTACHE SUR LE FOND DE LA CAVITE ET DECOLLE A NOUVEAU AU PASSAGE DU BORD AVAL DE LA CAVITE. L'ETUDE ACOUSTIQUE A PERMIS DE MONTRER QUE LE SPECTRE DU RAYONNEMENT ACOUSTIQUE DE CETTE CONFIGURATION ETAIT LARGE BANDE ET QU'IL N'APPARAISSAIT PAS D'OSCILLATION AERODYNAMIQUE OU ACOUSTIQUE. DIFFERENTES METHODES DE LOCALISATION ONT PERMIS DE MONTRER QUE LES SOURCES ACOUSTIQUES SE SITUAIENT PRINCIPALEMENT AU NIVEAU DU BORD AVAL DE LA CAVITE.

Download or read book Dynamique Non lin aire Et Le Chaos written by and published by . This book was released on 1993 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radioactive Aerosols written by Constantin Papastefanou and published by Elsevier. This book was released on 2011-07-28 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: Whenever radioactivity is released to the atmosphere, for example by the detonation of nuclear weapons or the testing of nuclear weapons or from nuclear reactor accidents that fraction of it which remains airborne for more than a few hours is liable to be attached to aerosol particles. The resulting radioactive aerosols are carried by atmospheric mixing processes until they settle out or are scavenged by precipitation. The radiation exposure pathway of maximum concern to humans is by inhalation of aerosols and their deposition in the respiratory tract. In this context, it is important to note that radioactive aerosols are commonly of natural origin alos. In particular, the associated radionuclides can be of natural terrestrial origin, such as the decay products of radon gas, or they can e cosmogenic, such as beryllium-7. The exposure of miners of uranium and other ores and minerals to radon and its aerosol-borne decay products is of major significance. The book describes the formation of aerosols, their aerodynamic size distribution, their atmospheric residence time, their sampling and measurement, the range of radioactive aerosols found and studied thus far, including man-made nuclides and radon decay products and their interaction with man, including deposition in the lung and subsequent health effects. - Advanced level science handbook for researchers, scientists and academics - Covers all aspects of radiation exposure in humans, including subsequent health implications - Presents the latest findings and analysis in this highly topical area

Download or read book Radiation Protection Activities written by United States. Environmental Protection Agency. Office of Radiation Programs and published by . This book was released on 1976 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Basic Radiation Protection Criteria written by and published by . This book was released on 1971 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Second International Conference on Artificial Neural Networks 18 20 November 1991 written by and published by . This book was released on 1991 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Second International Conference on Artificial Neural Networks was held November 1991 in the UK. Among the topics: theory, implementations, images, engineering applications, dynamical systems, control and robotics, hybrids, speech and natural language, medical applications, character recognition. No index. Annotation copyrighted by Book News, Inc., Portland, OR.

Download or read book Turbulent Mirror written by John Briggs and published by HarperCollins Publishers. This book was released on 1989 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explores the many faces of chaos and reveals how its laws direct most of the familiar processes of everyday life.

Download or read book Effects of Atomic Radiation written by William J. Schull and published by Wiley-Liss. This book was released on 1995-09-08 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting a monumental achievement: 50 years of data cataloging the immediate, long-term, and hereditary effects of atomic radiation on the survivors of the Hiroshima and Nagasaki bombs. Authored by one of the key members of the Atomic Bomb Casualty Commission founded in 1947, this unique work documents the critical findings and conclusions of the longest ongoing medical study in history; it will surely become the foundation for all future investigations and standards regarding the bioeffects of ionizing radiation. "In my opinion, Dr. Schull has written a very interesting and accurate account of the atomic bomb follow-up program in Japan. He writes extremely well, with areas of his particular scientific interest described in great detail. He also describes events and the social implications in a manner that has broad, general appeal." —Stuart C. Finch, MD University of Medicine and Dentistry of New Jersey "A history of the Hiroshima/Nagasaki study is badly needed. I was very happy to hear that Jack Schull was working on such a project, and it is an understatement to say that I am anxious to see it published." —Seymour Jablon, PhD Bethesda, Maryland "Rarely in the history of a program will one have a nearly 50-year account from an eyewitness and major participant, beginning with the program's onset to the present. Jack's book offers the reader this extraordinary insight into the birth and development of the study of the A-bomb survivors. Moreover, he has served on all major national and international commissions dealing with radiation protection and risk assessment and he interweaves the Japanese studies into the radiation risk issues in a way that few, if any, other contemporary scientists can." —Seymour Abrahamson, PhD Radiation Effects Research Foundation On August 6 and 9, 1945, the only atomic bombs ever used in warfare were dropped on the Japanese cities of Hiroshima and Nagasaki. The destruction and death caused by those bombings presented the world with a vivid portrait of the dangers of the atomic age. However, the thousands of bomb survivors have given scientists a massive, firsthand perspective on the bioeffects of radioactivity. It is the study of these survivors that forms the foundation of the modern understanding of the immediate, long-term, and hereditary consequences of exposure to ionizing radiation. Effects of Atomic Radiation: A Half-Century of Studies from Hiroshima and Nagasaki is the definitive account of the methods, findings, and conclusions of the 50-year study on the survivors of the atomic bomb blasts. It is a truly monumental work, surveying a colossal body of data to offer a comprehensive, unified, and authoritative summary of not only the scientific study itself, but the personal, social, and political factors that have shaped the investigation from its inception. The book goes beyond the simple compilation of facts, giving the reader unique insight into this unprecedented research project and exploring the complex web of subjective perceptions and fears that color popular, national, and even scientific views of radiation exposure in moderate and extreme cases. Authored by Dr. William J. Schull, perhaps the single most influential scientist involved in the studies, this book conveys both his authority and sensitivity. Dr. Schull arrived in Japan in 1949 and was instrumental in the development of the Atomic Bomb Casualty Commission. Since then, he has been one of the driving forces behind the largest medical follow-up study ever undertaken. His years spent working directly with bomb survivors imbue his narrative with a compelling personal history, and his service on numerous national and international committees studying ionizing radiation give him a broad, authoritative perspective on the implications of the ABCC's work. Effects of Atomic Radiation: A Half-Century of Studies from Hiroshima and Nagasaki is first and foremost a scientific work, summarizing the core findings of the definitive study on radiation exposure; while throughout the book, the author provides personal accounts that illustrate the human dimensions of the bombings. In a world where nuclear power is increasing and exposure to radiation is a daily occurrence, this book is essential reading for all scientists associated with public, private, or governmental institutions that set standards of acceptability for exposure.