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

P. C. CHATWIN
2002 European journal of applied mathematics  
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 fluctuations, eventually to zero. Arguments are presented which suggest that this quantity could,
more » ... is 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.
doi:10.1017/s0956792501004727 fatcat:qzi5jal4lrdqdb63kspr2z7sya