On the modelling of the transport equation for the passive scalar dissipation rate

Modelling of the passive scalar dissipation rate, eθ, is considered. Budgets of the passive scalar variance and its dissipation rate are presented using the DNS data of a turbulent channel flow, with an imposed mean scalar gradient, by Wikstrom & Johansson [10]. The Prandtl number is 0.71 and the Reynolds number based on the wall friction velocity, uτ, and the channel half width is 265. Comparison with the model of Sanders & Gokalp [7] is made together with model comparisons for the individual terms appearing in the transport equation of eθ.