Concept

Attracteur de Lorenz

L’attracteur de Lorenz est une structure fractale correspondant au comportement à long terme de l'oscillateur de Lorenz. L'attracteur montre comment les différentes variables du système dynamique évoluent dans le temps en une trajectoire non périodique. En 1963, le météorologue Edward Lorenz est le premier à mettre en évidence le caractère vraisemblablement chaotique de la météorologie. Le modèle de Lorenz, appelé aussi système dynamique de Lorenz ou oscillateur de Lorenz, est une modélisation simplifiée de phénomènes météorologiques basée sur la mécanique des fluides. Ce modèle est un système dynamique tridimensionnel qui engendre un comportement chaotique dans certaines conditions. Le modèle de Lorenz a eu des répercussions importantes en montrant les limites possibles sur la capacité de prédiction à long terme de l'évolution climatique et météorologique. C'est un élément important de la théorie selon laquelle l' des planètes et des étoiles peut comporter une grande variété de régimes quasi périodiques et est sujette à des changements abrupts et, en apparence, aléatoires. C'est aussi un exemple utile à la théorie des systèmes dynamiques servant de source à de nouveaux concepts mathématiques. L'attracteur et les équations associées ont été rendues publiques en 1963 par Edward Lorenz. Mathématiquement, le couplage de l'atmosphère terrestre avec l'océan est décrit par le système d'équations aux dérivées partielles couplées de Navier-Stokes de la mécanique des fluides. Ce système d'équations était beaucoup trop compliqué à résoudre numériquement pour les ordinateurs existant au temps de Lorenz. Celui-ci eut donc l'idée de chercher un modèle très simplifié de ces équations pour étudier une situation physique particulière : le phénomène de convection de Rayleigh-Bénard. Il aboutit alors à un système dynamique différentiel possédant seulement trois degrés de liberté, beaucoup plus simple à intégrer numériquement que les équations de départ. Ce système différentiel s'écrit : où σ, ρ et β sont trois paramètres strictement positifs, fixés.

Source officielle

https://fr.wikipedia.org/wiki/Attracteur_de_Lorenz

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Source officielle

https://fr.wikipedia.org/wiki/Attracteur_de_Lorenz

À propos de ce résultat

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