Mixing of discontinuously deforming media

Mixing of materials is fundamental to many natural phenomena and engineering applications. The presence of discontinuous deformations - such as shear banding or wall slip - creates new mechanisms for mixing and transport beyond those predicted by classical dynamical systems theory. Here we show how...

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Bibliographic Details
Published in:arXiv.org 2016-02
Main Authors: Smith, Lachlan D, Rudman, Murray, Lester, Daniel R, Metcalfe, Guy
Format: Article
Language:English
Subjects:
Chaos theory
Deformation mechanisms
Dynamic systems theory
Dynamical systems
Fluid dynamics
Fluid flow
Stretching
System theory
Wall slip
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Summary:Mixing of materials is fundamental to many natural phenomena and engineering applications. The presence of discontinuous deformations - such as shear banding or wall slip - creates new mechanisms for mixing and transport beyond those predicted by classical dynamical systems theory. Here we show how a novel mixing mechanism combining stretching with cutting and shuffling yields exponential mixing rates, quantified by a positive Lyapunov exponent, an impossibility for systems with cutting and shuffling alone or bounded systems with stretching alone, and demonstrate it in a fluid flow. While dynamical systems theory provides a framework for understanding mixing in smoothly deforming media, a theory of discontinuous mixing is yet to be fully developed. New methods are needed to systematize, explain and extrapolate measurements on systems with discontinuous deformations. Here we investigate 'webs' of Lagrangian discontinuities and show that they provide a template for the overall transport dynamics. Considering slip deformations as the asymptotic limit of increasingly localised smooth shear we also demonstrate exactly how some of the new structures introduced by discontinuous deformations are analogous to structures in smoothly deforming systems.
ISSN:2331-8422
DOI:10.48550/arxiv.1602.05245