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Author: Hugues Chaté
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Languages : fr
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Cette thèse regroupe des travaux analytiques et numériques sur le problème de la transition vers la turbulence des systèmes a grand rapport d'aspect pouvant présenter des régimes dynamiques ou coexistent et évoluent, dans le temps et l'espace, des régions ordonnées (laminaires) et désordonnées (turbulentes). Nous développons, pour ces régimes d'intermittence spatio-temporelle, une méthode d'analyse montrant que les transitions sont en général bien décrites en termes de transition de phase, ce qui constitue une irruption nouvelle de la mécanique statistique dans le champ de l'hydrodynamique. La première partie est consacrée a l'étude d'équations aux dérivées partielles non intégrables similaires au modèle de kuramoto-sivashinsky, qui peuvent être vues comme des modèles unidimensionnels de la convection de rayleigh-benard. La seconde partie traite de réseaux d'itérations couplées et présente les transitions d'un modèle minimal dans des espaces de dimension un a quatre. Cette étude montre que la transition vers la turbulence via intermittence spatio-temporelle n'est pas universelle au sens des classes d'universalité des phénomènes critiques. Dans la troisième partie, nous étudions des automates cellulaires relies au problème de la transition vers la turbulence via intermittence spatio-temporelle et proposons une explication de la non-universalité de la transition
Author: Hugues Chaté
Publisher:
ISBN:
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Languages : fr
Pages :
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Book Description
Cette thèse regroupe des travaux analytiques et numériques sur le problème de la transition vers la turbulence des systèmes a grand rapport d'aspect pouvant présenter des régimes dynamiques ou coexistent et évoluent, dans le temps et l'espace, des régions ordonnées (laminaires) et désordonnées (turbulentes). Nous développons, pour ces régimes d'intermittence spatio-temporelle, une méthode d'analyse montrant que les transitions sont en général bien décrites en termes de transition de phase, ce qui constitue une irruption nouvelle de la mécanique statistique dans le champ de l'hydrodynamique. La première partie est consacrée a l'étude d'équations aux dérivées partielles non intégrables similaires au modèle de kuramoto-sivashinsky, qui peuvent être vues comme des modèles unidimensionnels de la convection de rayleigh-benard. La seconde partie traite de réseaux d'itérations couplées et présente les transitions d'un modèle minimal dans des espaces de dimension un a quatre. Cette étude montre que la transition vers la turbulence via intermittence spatio-temporelle n'est pas universelle au sens des classes d'universalité des phénomènes critiques. Dans la troisième partie, nous étudions des automates cellulaires relies au problème de la transition vers la turbulence via intermittence spatio-temporelle et proposons une explication de la non-universalité de la transition
Author: SABINE.. BOTTIN
Publisher:
ISBN:
Category :
Languages : fr
Pages : 240
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Book Description
CETTE THESE CONCERNE L'ETUDE EXPERIMENTALE DE LA TRANSITION VERS LA TURBULENCE DANS LE CAS DE L'ECOULEMENT DE COUETTE PLAN. CET ECOULEMENT EST LINEAIREMENT STABLE POUR TOUT NOMBRE DE REYNOLDS ET, LORSQU'IL EST PERTURBE, UNE COEXISTENCE ENTRE L'ETAT LAMINAIRE ET L'ETAT TURBULENT PEUT ETRE OBSERVEE. NOUS MONTRONS A L'AIDE D'UNE PERTURBATION LOCALISEE ET PERMANENTE -UN FIL PERPENDICULAIRE A L'ECOULEMENT- QUE LES STRUCTURES COHERENTES DE ROULEAUX LONGITUDINAUX CONTRA-ROTATIFS PRESENTES AUTOUR DU FIL SONT IDENTIQUES A CELLES OBSERVEES EN BORDURE DE SPOTS, ET QUE CE SONT DES SOLUTIONS D'AMPLITUDES FINIES DANS LA LIMITE DE L'ECOULEMENT DE COUETTE PLAN NON MODIFIE. UN GEL SPATIAL DE LA DYNAMIQUE DE CES ROULEAUX A ETE REALISE A L'AIDE D'UN PETIT OBSTACLE -UNE PERLE- INSTALLE AU CENTRE DE L'ECOULEMENT. LE COMPORTEMENT INTERMITTENT OBSERVE EST REVELATEUR D'UNE DYNAMIQUE SOUS-JACENTE DE CHAOS SPATIO-TEMPOREL POUR LE SYSTEME NON PERTURBE. POUR ETUDIER LA TRANSITION, NOUS UTILISONS DES PERTURBATIONS INSTANTANEES D'AMPLITUDE VARIABLE ET DES TREMPES EN R. NOUS OBSERVONS UN REGIME D'INTERMITTENCE SPATIO-TEMPORELLE (IST) ET CARACTERISONS UN NOMBRE DE REYNOLDS CRITIQUE, R#C, AU DESSUS DUQUEL L'IST EST PERSISTANTE ET LA FRACTION TURBULENTE MOYENNE BIEN DEFINIE CROIT AVEC R. UN ATTRACTEUR TURBULENT UNIQUE COEXISTE AVEC L'ECOULEMENT LAMINAIRE, ET UNE DEFINITION PROPRE D'UNE COURBE D'AMPLITUDE CRITIQUE EST DONNEE. EN DESSOUS DE R#C, IL EXISTE DES TRANSITOIRES LONGS QUI RELAXENT VERS L'ETAT LAMINAIRE ; L'ATTRACTEUR EST TRANSFORME EN UN REPULSEUR CHAOTIQUE. CETTE ETUDE A ETE ENTREPRISE D'UN POINT DE VUE STATISTIQUE ET GUIDEE PAR L'ETUDE PARALLELE D'UN MODELE NUMERIQUE SIMPLE DE RESEAU D'ITERATIONS COUPLES POUR L'IST. CETTE TRANSITION VERS L'IST EST IDENTIFIEE COMME DISCONTINUE.
Author: Tom Mullin
Publisher: Springer Science & Business Media
ISBN: 1402040490
Category : Technology & Engineering
Languages : en
Pages : 335
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Book Description
An exciting new direction in hydrodynamic stability theory and the transition to turbulence is concerned with the role of disconnected states or finite amplitude solutions in the evolution of disorder in fluid flows. This volume contains refereed papers presented at the IUTAM/LMS sponsored symposium on "Non-Uniqueness of Solutions to the Navier-Stokes equations and their Connection with Laminar-Turbulent Transition" held in Bristol 2004. Theoreticians and experimentalists gathered to discuss developments in understanding both the onset and collapse of disordered motion in shear flows such as those found in pipes and channels. The central objective of the symposium was to discuss the increasing amount of experimental and numerical evidence for finite amplitude solutions to the Navier-Stokes equations and to set the work into a modern theoretical context. The participants included many of the leading authorities in the subject and this volume captures much of the flavour of the resulting stimulating and lively discussions.
Author: Paul Manneville
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
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Book Description
This lecture presented a scenario of transition to turbulence specific to large aspect ratio systems. Starting with simulations on a model chosen for its relevance to the field of convective instabilities we characterized the spatio-temporal intermittent 'phase'. Then we examined the transition process having recourse to simpler systems: coupled maps lattices. This process appeared to involve the propagation of an information, laminar/turbulent which seemed stochastic though it was generated by a deterministic dynamics. Concepts first introduced in the statistical physics of critical phenomena applied to directed percolation allowed us to account for most features of spatio-temporal intermittency, and especially the change of behavior at what turned out to be a true threshold. The implications of this approach are important because, in large aspect ratio systems, we have to face the possibility that what we think is turbulence may be simply a finite life-time but very long turbulent transient. If the percolation analogy is valid, then a threshold exists above which the turbulent state percolates through the system and turbulence has virtually no chance to decay.
Author: Rama Govindarajan
Publisher: Springer Science & Business Media
ISBN: 1402041594
Category : Technology & Engineering
Languages : en
Pages : 466
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Book Description
The dynamics of transition from laminar to turbulent flow remains to this day a major challenge in theoretical and applied mechanics. A series of IUTAM symposia held over the last twenty five years at well-known Centres of research in the subject - Novosibirsk, Stuttgart, Toulouse, Sendai and Sedona (Arizona) - has proved to be a great catalyst which has given a boost to research and our understanding of the field. At this point of time, the field is changing significantly with several emerging directions. The sixth IUTAM meeting in the series, which was held at the Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India, focused on the progress after the fifth meeting held at Sedona in 1999. The s- posium, which adhered to the IUTAM format of a single session, included seven invited lectures, fifty oral presentations and eight posters. During the course of the symposium, the following became evident. The area of laminar-turbulent transition has progressed considerably since 1999. Better theoretical tools, for handling nonlinearities as well as transient behaviour are now available. This is accompanied by an en- mous increase in the level of sophistication of both experiments and direct numerical simulations. The result has been that our understanding of the early stages of the transition process is now on much firmer footing and we are now able to study many aspects of the later stages of the transition process.
Author: Bailin Hao
Publisher: World Scientific
ISBN: 9814507113
Category : Science
Languages : en
Pages : 476
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Book Description
This is a continuation of the previous two volumes of review papers on chaotic dynamics and related topics, published in 1987 and 1988 respectively. In addition to a few reviews written by active researchers specially for the volume, it also contains several reviews based on lectures delivered at the Spring School on Experimental Study of Chaotic Phenomena, held in Tianjing, China, in May 1989, and at the session on Nonlinear Dynamics during the Workshop on Condensed Matter, Molecular and Atomic Physics, held in June - August, 1989, at the International Centre for Theoretical Physics at Trieste, Italy. The emphasis has been made on multifractals, applied symbolic dynamics, the role of unstable orbits and transient chaos. This volume would be useful to graduate students and researchers in physical sciences and engineering.
Author: G. Nicolis
Publisher: Cambridge University Press
ISBN: 9780521467827
Category : Mathematics
Languages : en
Pages : 274
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Book Description
The aim of this book is to develop a unified approach to nonlinear science, which does justice to its multiple facets and to the diversity and richness of the concepts and tools developed in this field over the years. Nonlinear science emerged in its present form following a series of closely related and decisive analytic, numerical and experimental developments that took place over the past three decades. It appeals to an extremely large variety of subject areas, but, at the same time, introduces into science a new way of thinking based on a subtle interplay between qualitative and quantitative techniques, topological and metric considerations and deterministic and statistical views. Special effort has been made throughout the book to illustrate both the development of the subject and the mathematical techniques, by reference to simple models. Each chapter concludes with a set of problems. This book will be of great value to graduate students in physics, applied mathematics, chemistry, engineering and biology taking courses in nonlinear science and its applications.
Author: FRANCOIS.. DAVIAUD
Publisher:
ISBN:
Category :
Languages : fr
Pages :
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Book Description
NOUS ETUDIONS LES PROPRIETES SPATIO-TEMPORELLES ET LA TRANSITION A LA TURBULENCE DANS DES SYSTEMES D'ECOULEMENTS CONVECTIFS DE RAYLEIGH-BENARD POSSEDANT UNE OU DEUX DIMENSIONS D'ESPACE. LA PREMIERE PARTIE EST CONSACREE A L'ETUDE DE SYSTEMES CONVECTIFS UNIDIMENSIONNELS. ELLE REVELE L'EXISTENCE DE COMPORTEMENTS DYNAMIQUES COLLECTIFS, PUIS UNE TRANSITION VERS LA TURBULENCE VIA UN PHENOMENE D'INTERMITTENCE SPATIO-TEMPOREL CARACTERISE PAR LA COEXISTENCE DE REGIONS ORDONNEES (LAMINAIRES) ET DESORDONNEES (TURBULENTES), QUI EVOLUENT DANS LE TEMPS ET DANS L'ESPACE. NOUS MONTRONS PAR UNE ETUDE STATISTIQUE QUE CETTE EVOLUTION PEUT ETRE DECRITE EN TERMES DE TRANSITION DE PHASE ET QU'ELLE EST SIMILAIRE A LA TRANSITION OBSERVEE DANS CERTAINS MODELES NUMERIQUES, NOTAMMENT EN PERCOLATION DIRIGEE. LA SECONDE PARTIE CONCERNE L'ETUDE DES ROUTES VERS LA TURBULENCE QUI SONT OBSERVEES DANS DES GEOMETRIES ETENDUES ET A FAIBLE NOMBRE DE PRANDTL. LES RESULTATS EXPERIMENTAUX SONT PRESENTES PUIS INTERPRETES DANS LE CADRE D'UN FORMALISME UTILISANT LES EQUATIONS DE PHASE. ILS MONTRENT L'INTERACTION EXISTANT ENTRE LES COURANTS A GRANDE ECHELLE ET LES ECOULEMENTS CONVECTIFS, ET METTENT EN EVIDENCE L'INFLUENCE DES CONDITIONS AUX LIMITES SUR L'EVOLUTION DES STRUCTURES CONVECTIVES
Author: E. Tirapegui
Publisher: Springer Science & Business Media
ISBN: 9401142475
Category : Science
Languages : en
Pages : 404
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Book Description
This book contains two introductory papers on important topics of nonlinear physics. The first one, by M. San Miguel et al., refers to the effect of noise in nonequilibrium systems. The second, by M.E. Brachet, is a modern introduction to turbulence in fluids. The material can be very useful for short courses and is presented accordingly. The authors have made their texts self-contained. The volume also contains a selection of the invited seminars given at the Sixth International Workshop on Instabilities and Nonequilibrium Structures. Audience: This book should be of interest to graduate students and scientists interested in the fascinating problems of nonlinear physics.
Author: Tapan K. Sengupta
Publisher: Cambridge University Press
ISBN: 1108490417
Category : Technology & Engineering
Languages : en
Pages : 643
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Book Description
"Present understanding of transition to turbulence has now been studied over one hundred and fifty years. The path the studies have taken posed it as a modal eigenvalue problem. Some researchers have suggested alternative models without being specific. First-principle based approach of receptivity is the route to build bridges among ideas for solving the Navier-Stokes equation for specific canonical problems. This book highlights the mathematical physics, scientific computing, and new ideas and theories for nonlinear analyses of fluid flows, for which vorticity dynamics remain central. This book is a blend of classic with distinctly new ideas, which establish different dynamics of flows, from genesis to evolution of disturbance fields with rigorously developed methods to tracing coherent structures amidst the seemingly random and chaotic fluid dynamics of transitional and turbulent flows"--
