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Large-scale effects on meso-scale modeling for scalar transport
Full text linkThe transport of scalar quantities passively advected by velocity fields with a component at small scale l can be modeled at scales larger than l by means of an effective drift and an effective diffusivity, which can be determined by means of multiple-scale techniques. We show that the presence of a weak flow at large scales L >> l induces interesting effects on the scalar transport at the meso-scales (i.e. at scales intermediate between l and L). In particular, it gives rise to non-isotropic and non-homogeneous corrections to the meso-scale drift and diffusivity. We discuss an approximation that allows us to retain the second-order effects caused by the large-scale flow. This provides a rather accurate meso-scale modeling for both asymptotic and pre-asymptotic scalar transport properties. Numerical simulations in model flows are used to illustrate the importance of such large-scale effects. (c) 2006 Elsevier B.V. All rights reserved
Chaos: from simple models to complex systems
No full textChaos: from simple models to complex systems aims to guide science and engineering students through chaos and nonlinear dynamics from classical examples to the most recent fields of research. The first part, intended for undergraduate and graduate students, is a gentle and self-contained introduction to the concepts and main tools for the characterization of deterministic chaotic systems, with emphasis to statistical approaches. The second part can be used as a reference by researchers as it focuses on more advanced topics including the characterization of chaos with tools of information theo
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