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Accelerated diffusion in the centre of a vortex

Citation

Bajer, K and Bassom, AP and Gilbert, AD, Accelerated diffusion in the centre of a vortex, Journal of Fluid Mechanics, 437 pp. 395-411. ISSN 0022-1120 (2001) [Refereed Article]

Copyright Statement

Copyright 2001 Cambridge University Press

DOI: doi:10.1017/S0022112001004232

Abstract

The spiral wind-up and diffusive decay of a passive scalar in circular streamlines is considered. An accelerated diffusion mechanism operates to destroy scalar fluctuations on a time scale of order P1/3 times the turn-over time, where P is a Péclet number. The mechanism relies on differential rotation, that is, a non-zero gradient of angular velocity. However if the flow is smooth, the gradient of angular velocity necessarily vanishes at the centre of the streamlines, and the time scale becomes greater. The behaviour at the centre is analysed and it is found that scalar there is only destroyed on a time scale of order P1/2. Related results are obtained for magnetic field and for weak vorticity, a scalar coupled to the stream function of the flow. Some exact solutions are presented.

Item Details

Item Type:Refereed Article
Research Division:Mathematical Sciences
Research Group:Applied Mathematics
Research Field:Theoretical and Applied Mechanics
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Mathematical Sciences
Author:Bassom, AP (Professor Andrew Bassom)
ID Code:107122
Year Published:2001
Web of Science® Times Cited:49
Deposited By:Mathematics and Physics
Deposited On:2016-03-04
Last Modified:2016-07-08
Downloads:0

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