A new method of modeling the conditional scalar dissipation rate

Abstract

A new method for calculating the conditional scalar dissipation rate 〈N|η〉 is derived from the probability density function (pdf) transport equation for the conserved scalar Z. Two different formulations are obtained. One is the result of direct integration of the pdf transport equation and the second is further developed assuming a two-parameter presumed form for the pdf. A linear model is used for the conditional velocity. The model is compared with a direct numerical simulation (DNS) of inhomogeneous turbulent mixing. The results are in very good agreement with the DNS and perform better than Girimaji’s model which is based on homogeneous flow properties. Further validation with some experimental data would be useful. The new method has also the potential of being easily implemented in a finite-volume computational fluid dynamics code.