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Some remarks on modelling the PDF of the concentration of a dispersing scalar in turbulence

Published online by Cambridge University Press:  16 April 2002

P. C. CHATWIN
Affiliation:
Department of Applied Mathematics, University of Sheffield, Hicks Building, Sheffield S3 7RH, UK

Abstract

The paper deals with the probability density function (PDF) of the concentration of a scalar within a turbulent flow. Following some comments about the overall structure of the PDF, and its approach to a limit at large times, attention focusses on the so-called small scale mixing term in the evolution equation for the PDF. This represents the effect of molecular diffusion in reducing concentration uctuations, eventually to zero. Arguments are presented which suggest that this quantity could, in certain circumstances, depend inversely upon the PDF, and a particular example of this leads to a new closure hypothesis. Consequences of this, especially similarity solutions, are explored for the case when the concentration field is statistically homogeneous.

Type
Research Article
Copyright
2002 Cambridge University Press

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