Mixing of a conserved scalar in a turbulent shear layer

in studying values of the rate of scalar dissipation that mark the boundary between flames that feel a constant scalar dissipation field and those that do not. 1. Introduction Acommon approach in the modelling of non-premixed turbulent combustion is based on knowledge of two variables: a mixture fraction, Z,thatrepresents the mixture composition, giving the fraction of the material that comes from the fuel stream; and its so-called scalar dissipation, # =2D#Z #Z (in which D is its molecular di#usivity), # being related to the rate of dissipation of fluctuations of Z in turbulent flow. Since many chemical length scales are often several orders of magnitude smaller than the turbulent length scales in real applications, modelling of Z with a thin reaction sheet at its stoichiometric surface can be a reasonable approach that helps to separate the chemistry from the turbulence. Knowledge of Z and # in turbulent flows is important for testing the validity of various models, such as the