Graduate School in Nonlinear Science

Sponsored by the Danish Research Academy

MIDIT                               OFD                           CATS
Modelling, Nonlinear Dynamics       Optics and Fluid Dynamics     Chaos and Turbulence Studies
and Irreversible Thermodynamics     Risø National Laboratory      Niels Bohr Institute and 
Technical University of Denmark     Building 128                  Department of Chemistry
Building 321                        P.O. Box 49                   University of Copenhagen 
DK-2800 Lyngby                      DK-4000 Roskilde              DK-2100 Copenhagen Ø
Denmark                             Denmark                       Denmark


by Dr. Mark Stremler
Department of Theoretical and Applied Mechanics,
University of Illinois at Urbana-Champaign, USA

MIDIT-seminar 476

Wednesday March 01, 2000, 15.15 h
at MIDIT, MAT, Bldg. 303, Room 026, DTU,

Abstract: A new approach to regular and chaotic fluid advection will be presented that utilizes the Thurston-Nielsen classification theorem. The prototypical 2D problem of stirring by a finite number of stirrers confined to a disk of fluid will be considered. The theory shows that for particular 'stirring protocols' a significant increase in complexity of the stirred motion -- known as topological chaos -- occurs when three or more stirrers are present and are moved about in certain ways. The basic theory will be set out without proofs, and the applicability of several topological concepts to fluid stirring will be demonstrated. A simple experiment in which a viscous liquid is stirred by three stirrers has been conducted and will be used to illustrate the theory.