Download or read book Contribution l tude des instabilit s dans les jets plans par simulation num rique written by Florence Sers and published by . This book was released on 1995 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: CE TRAVAIL CONTRIBUE A UNE MEILLEURE COMPREHENSION DES MECANISMES D'APPARITION ET DE DEVELOPPEMENT DES INSTABILITES NON-VISQUEUSES DANS UNE CONFIGURATION DE JET LIBRE PLAN. DEUX ECOULEMENENTS SONT TRAITES AU MOYEN DE LA SIMULATION NUMERIQUE: LE JET ISOTHERME ET LE JET CHAUFFE. POUR CHACUN DE CES DEUX ECOULEMENTS, ON S'ATTACHE A RECONNAITRE ET A ANALYSER LA NATURE CONVECTIVE OU ABSOLUE (GLOBALE) DE L'INSTABILITE. L'EXISTENCE D'UN FEED-BACK DE PRESSION ISSU DE L'INTERACTION NON-LINEAIRE ROTATIONEL-ROTATIONEL EST DEMONTREE SUR LE JET ISOTHERME. L'INFLUENCE DE LA FORME DU PROFIL INITIAL DE VITESSE SUR LA CARACTERISATION DE LA NATURE DE L'INSTABILITE EST EGALEMENT PROUVEE. LES TESTS EFFECTUES SUR UN PROFIL DE VITESSE CARRE REVELENT QUE CE PROFIL N'EST PAS JUDICIEUX POUR METTRE EN EVIDENCE LE CARACTERE CONVECTIVEMENT INSTABLE DU JET ISOTHERME. IL CONVIENT D'UTILISER UN PROFIL PLUS DOUX COMME LE PROFIL EN SINUS HYPERBOLIQUE. ENFIN, ON MONTRE QUE L'ON PEUT DETERMINER UN MODE GLOBAL AUTO-ENTRETENU DANS LE JET CHAUFFE POURVU QUE LE RAPPORT DE DENSITE, A RAPPORT DE VITESSE R DE 0,93 ET NOMBRE DE MACH M DE 0,15, SOIT INFERIEUR A 0,5. L'EVOLUTION DE L'AMPLITUDE DE CE MODE GLOBAL SUIVANT LE RAPPORT DE DENSITE INDIQUE QUE L'ECOULEMENT GENERE UN ETAT DYNAMIQUE AUTO-ENTRETENU VIA UNE BIFURCATION DE HOPF. LES EFFETS DU NOMBRE DE MACH SUR L'APPARITION DU MODE GLOBAL DANS L'ECOULEMENT SONT EGALEMENT ABORDES. ON PROUVERA QUE LE CODE DE CALCUL UTILISE CONSTITUE UN BON OUTIL D'ANALYSE DES PHENOMENES D'INSTABILITE LINEAIRES ET NON-LINEAIRES DANS LE CAS D'ECOULEMENTS FORTEMENT CISAILLES

Download or read book Etude des instabilit s d un jet plan masse volumique variable written by Stéphane Ravier and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'influence de la variation de masse volumique pour le développement des instabilités primaires d'un jet plan est étudiée par simulation numérique directe des équations de Navier-Stokes incompressibles. Chaque méthode numérique retenue ainsi que la construction du programme sont détaillées pas à pas en insistant particulièrement sur le choix des conditions aux limites. La méthode est validée par une étude linéaire qui présente des résultats pour une large gamme de valeurs du rapport de densité. À partir de ce code non linéaire, on étudie la transition convective/absolue subie par le mode variqueux lorsque le rapport de densité diminue pour différents profils dont le Bickley et le presque top-hat. Une remise en cause du critère de stabilité marginale est proposée. En outre, l'observation inattendue de modes globaux amortis pour les rapports de densité voisins de 1 dans le cas d'un profil presque top-hat nous conduit à proposer une hypothèse en étudiant l'équation analytique implicite qui définit la relation de dispersion du mode variqueux pour un profil top-hat. Une courte étude expérimentale dans laquelle on présente les différentes techniques employées, ainsi que les premières mesures de vitesse et de densité, complète ce travail, en donnant des informations sur les fréquences caractéristiques.

Download or read book Turbulence in Fluids written by Marcel Lesieur and published by Springer Science & Business Media. This book was released on 2008-03-26 with total page 593 pages. Available in PDF, EPUB and Kindle. Book excerpt: Now in its fully updated fourth edition, this leading text in its field is an exhaustive monograph on turbulence in fluids in its theoretical and applied aspects. The authors examine a number of advanced developments using mathematical spectral methods, direct-numerical simulations, and large-eddy simulations. The book remains a hugely important contribution to the literature on a topic of great importance for engineering and environmental applications, and presents a very detailed presentation of the field.

Download or read book 29th AIAA Fluid Dynamics Conference written by and published by . This book was released on 1998 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Contribution l tude de la simulation num rique de la turbulence written by MICHEL.. BOURIOT and published by . This book was released on 1984 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: LA RESOLUTION NUMERIQUE DES EQUATIONS BIDIMENSIONNELLES ET INSTATIONNAIRES DE NAVIER-STOKES, SOUS FORME FONCTION DE COURANT-TOURBILLON EST EFFECTUEE PAR UNE METHODE AUX DIFFERENCES FINIES DU SECOND ORDRE ET POUR DEUX TYPES D'ECOULEMENTS CISAILLES: SILLAGES ET COUCHES DE MELANGE. RESULTATS CONCERNANT UNE VISUALISATION RALENTIE DU COMPORTEMENT DES CHAMPS DE TOURBILLON ET DE VITESSE, L'ETUDE DU DEVELOPPEMENT SPATIOTEMPOREL D'INSTABILITES DANS UNE COUCHE CISAILLEE AINSI QUE LA MISE EN EVIDENCE D'UN EFFET MODERATEUR DE LA TURBULENCE DANS UN MELANGE EN REGIME DE TRANSITION, SOUMMIS A UNE EXCITATION SUR SON MODE PROPRE DE PERTURBATION. SCHEMA DE CALCUL PRECIS POUR LA PRESSION

Download or read book Instabilit d un jet confin written by Agnès Maurel and published by . This book was released on 1994 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: UNE ETUDE EXPERIMENTALE ET NUMERIQUE EST MENEE SUR L'OSCILLATION AUTO-ENTRETENUE D'UN JET BIDIMENSIONNEL DANS UNE CAVITE RECTANGULAIRE. L'ETUDE EXPERIMENTALE PERMET DE PRECISER LES DIFFERENTS REGIMES OBSERVES LORSQUE LA VITESSE D'ENTREE DU JET ET LA LONGUEUR DE LA CAVITE VARIENT. UNE ETUDE PLUS DETAILLEE DU REGIME D'OSCILLATIONS AUTO-ENTRETENUES EST PRESENTEE. ELLE MET EN EVIDENCE L'EXISTENCE DE MODES (STAGES), CARACTERISES PAR UNE LONGUEUR D'ONDE CONSTANTE VERIFIANT L=(N+1/4), OU L EST LA LONGUEUR DE LA CAVITE ; LA VALEUR N SELECTIONNEE DEPEND DE LA LARGEUR D'ENTREE DU JET ET DE LA VITESSE D'ENTREE DU JET. LE MECANISME D'AMPLIFICATION PRESUME EST FONDE SUR UN MODELE DE SYNCHRONISATION ENTRE L'OSCILLATION A LA SORTIE DE LA CAVITE ET LES PERTURBATIONS DECLENCHEES A L'ENTREE DU JET. L'ETUDE NUMERIQUE EST MENEE SUR UNE CAVITE CARREE (LES SIMULATIONS 2D SONT EFFECTUEES AVEC LE CODE DE CALCUL NEKTON, FONDE SUR UNE METHODE D'ELEMENTS FINIS SPECTRAUX) ET S'ATTACHE A DECRIRE L'INSTABILITE PROCHE DU SEUIL. UNE FREQUENCE FONDAMENTALE EST DEGAGEE EN REGIME LINEAIRE ET LES NON-LINEARITES FONT APPARAITRE L'HARMONIQUE 2 ET UN MODE STATIONNAIRE DE FREQUENCE NULLE ; ELLE MODIFIE LE MOTIF DE L'ECOULEMENT MOYEN. LE DEVELOPPEMENT DE CET ECOULEMENT MOYEN EST LE MECANISME DE SATURATION DE L'INSTABILITE OSCILLANTE: IL STABILISE LES PROFILS DE VITESSE. UNE METHODE D'ANALYSE EN MODES EST PRESENTEE, QUI TENTE DE DEGAGER DES GRANDEURS CARACTERISTIQUES DE L'INSTABILITE. LES METHODES D'EXPLOITATION DES RESULTATS DES SIMULATIONS SONT APPLICABLES DANS D'AUTRES GEOMETRIES ET, EN PARTICULIER, LES RESULTATS PRESENTES DANS CETTE THESE SONT COMPARABLES A CEUX MIS EN EVIDENCE DANS DES ETUDES NUMERIQUES DU SILLAGE

Download or read book Government reports annual index written by and published by . This book was released on 199? with total page 1600 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Large Eddy Simulations of Turbulence written by M. Lesieur and published by Cambridge University Press. This book was released on 2005-08-22 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.

Download or read book Advances in Turbulence VII written by Uriel Frisch and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 630 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Turbulence VII contains an overview of the state of turbulence research with some bias towards work done in Europe. It represents an almost complete collection of the invited and contributed papers delivered at the Seventh European Turbulence Conference, sponsored by EUROMECH and ERCOFTAC and organized by the Observatoire de la Côte d'Azur. New high-Reynolds number experiments combined with new techniques of imaging, non-intrusive probing, processing and simulation provide high-quality data which put significant constraints on possible theories. For the first time, it has been shown, for a class of passive scalar problems, why dimensional analysis sometimes gives the wrong answers and how anomalous intermittency corrections can be calculated from first principles. The volume is thus geared towards specialists in the area of flow turbulence who could not attend the conference as well as anybody interested in this rapidly moving field.

Download or read book Turbulence written by Uriel Frisch and published by Cambridge University Press. This book was released on 1995-11-30 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook presents a modern account of turbulence, one of the greatest challenges in physics. The state-of-the-art is put into historical perspective five centuries after the first studies of Leonardo and half a century after the first attempt by A. N. Kolmogorov to predict the properties of flow at very high Reynolds numbers. Such 'fully developed turbulence' is ubiquitous in both cosmical and natural environments, in engineering applications and in everyday life. The intended readership for the book ranges from first-year graduate students in mathematics, physics, astrophysics, geosciences and engineering, to professional scientists and engineers. Elementary presentations of dynamical systems ideas, of probabilistic methods (including the theory of large deviations) and of fractal geometry make this a self-contained textbook.

Download or read book The Mediterranean region under climate change written by Collectif and published by IRD Éditions. This book was released on 2018-11-19 with total page 736 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book has been published by Allenvi (French National Alliance for Environmental Research) to coincide with the 22nd Conference of Parties to the United Nations Framework Convention on Climate Change (COP22) in Marrakesh. It is the outcome of work by academic researchers on both sides of the Mediterranean and provides a remarkable scientific review of the mechanisms of climate change and its impacts on the environment, the economy, health and Mediterranean societies. It will also be valuable in developing responses that draw on “scientific evidence” to address the issues of adaptation, resource conservation, solutions and risk prevention. Reflecting the full complexity of the Mediterranean environment, the book is a major scientific contribution to the climate issue, where various scientific considerations converge to break down the boundaries between disciplines.

Download or read book ICREEC 2019 written by Ahmed Belasri and published by Springer Nature. This book was released on 2020-06-10 with total page 659 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights peer reviewed articles from the 1st International Conference on Renewable Energy and Energy Conversion, ICREEC 2019, held at Oran in Algeria. It presents recent advances, brings together researchers and professionals in the area and presents a platform to exchange ideas and establish opportunities for a sustainable future. Topics covered in this proceedings, but not limited to, are photovoltaic systems, bioenergy, laser and plasma technology, fluid and flow for energy, software for energy and impact of energy on the environment.

Download or read book Acoustics Aeroacoustics and Vibrations written by Fabien Anselmet and published by John Wiley & Sons. This book was released on 2016-01-07 with total page 529 pages. Available in PDF, EPUB and Kindle. Book excerpt: This didactic book presents the main elements of acoustics, aeroacoustics and vibrations. Illustrated with numerous concrete examples linked to solid and fluid continua, Acoustics, Aeroacoustics and Vibrations proposes a selection of applications encountered in the three fields, whether in room acoustics, transport, energy production systems or environmental problems. Theoretical approaches enable us to analyze the different processes in play. Typical results, mostly from numerical simulations, are used to illustrate the main phenomena (fluid acoustics, radiation, diffraction, vibroacoustics, etc.).

Download or read book Pension Reform and the Development of Pension Systems written by Emily S. Andrews and published by World Bank Publications. This book was released on 2006 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Formal pension systems are an important means of reducing poverty among the aged. In recent years, however, pension reform has become a pressing matter, as demographic aging, poor administration, early retirement, and unaffordable benefits have strained pension balances and overall public finances. Pension systems have become a source of macroeconomic instability, a constraint to economic growth, and an ineffective and/or inequitable provider of retirement income."

Download or read book Philosophy manual a South South perspective written by Chanthalangsy, Phinith and published by UNESCO Publishing. This book was released on 2014-12-31 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book IUTAM Symposium on Variable Density Low Speed Turbulent Flows written by Louis Fulachier and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: The General Assembly of the International Union of Theoretical and Applied Mechanics in its meeting on August 28, 1994, selected for 1996 only four Mechanics Symposia, of which ours is the only one related to Fluid Mechanics: Variable Density Low Speed Turbulent Flows. This IUTAM Symposium, organized by the Institut de Recherche sur les Phenomenes Hors Equilibre (Marseille), is the logical continuation of the meetings previously organized or co-organized - on the French or European level, such as Euromech 237, Marseille, 1988 - by the same research group ofMarseille. This meeting focused specifically on the structure of turbulent flows in which density varies strongly : the effect of this variation on the velocity and scalar fields is in no sense negligible. We were mainly concerned with low-speed flows subjected to strong local changes of density as a consequence of heat or mass transfer or of chemical reactions. Compressible turbulent flows - such a!" supersonic ones - were also considered in order to underline their similarities to and their differences from low-speed variable density flows.

Download or read book Basic Concepts for Simple and Complex Liquids written by Jean-Louis Barrat and published by Cambridge University Press. This book was released on 2003-03-27 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting a unified approach, this book focusses on the concepts and theoretical methods that are necessary for an understanding of the physics and chemistry of the fluid state. The authors do not attempt to cover the whole field in an encyclopedic manner. Instead, important ideas are presented in a concise and rigorous style, and illustrated with examples from both simple molecular liquids and more complex soft condensed matter systems such as polymers, colloids, and liquid crystals.