Universal behaviour of entrainment due to coherent structures in turbulent shear flow
Abstract
I suggest a solution to a persistent mystery in the physics of turbulent shear flows: cumulus clouds rise to towering heights, practically without entraining the ambient medium, while apparently similar turbulent jets in general lose their identity within a small distance through entrainment and mixing. From dynamical systems computations on a model chaotic vortical flow, I show that entrainment and mixing due to coherent structures depend sensitively on the relative speeds of different portions of the flow. A small change in these speeds, effected for example by heating, drastically alters the sizes of the KAM tori and the chaotic mixing region. The entrainment rate and, hence, the lifetime of a turbulent shear flow, shows a universal, non-monotone dependence on the heating.
Keywords
Cite
@article{arxiv.nlin/0202061,
title = {Universal behaviour of entrainment due to coherent structures in turbulent shear flow},
author = {Rama Govindarajan},
journal= {arXiv preprint arXiv:nlin/0202061},
year = {2009}
}
Comments
Preprint replaced in order to add the following comment: accepted for publication in Phys. Rev. Lett