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 David C. Montgomery
Dartmouth, USA

Wednesday October 13, 1999, 10:30 h
NBI, University of Copenhagen

Abstract: Most theoretical considerations of turbulence have been set in the "homogeneous turbulence" framework, in which spatially periodic boundary conditions are assumed for all time over a very large box with rectangular symmetry. Rather different results emerge when turbulent decays are computed inside rigid no-slip or stress-free material boundaries. Particularly in the two-dimensional case, it is possible to argue that no material container, however large, will ever lead to the same results as are now regularly seen in periodic geometry. One reason is the dominant role that angular momentum (nearly conserved by circular walls, generated by rectangular ones) seems to play in governing the decay. Computations at higher Reynolds numbers than have been carried out so far seem to be desirable. There are also unresolved problems associated with determinations of the pressure.

References: Shuojun Li, David Montgomery, and Wesley Jones, Theoretical and Computational Fluid Dynamics 9, 167 (1997); and Physics Letters A218, 281 (1996).