MODELING OF ISOTROPIC REACTING TURBULENCE BY A HYBRID MAPPING-EDQNM CLOSURE

A hybrid model is developed and implemented for predicting the limiting bound of the reactant conversion rate in an isotropic turbulent flow under the influence of a reaction of the type A + B --> Products. This model is based on the amplitude mapping closure of Kraichnan for the molecular mixing of a stochastically distributed scalar, and the eddy-damped quasi-normal Markovian (EDQNM) spectral closure for the two-point scalar covariance. The results predicted by this model compare well with available experimental data in both gaseous and aqueous plug-flow reactors, but point to the need for more detailed measurements in future experimental studies. With the implementation of the mapping closure, a simple analytical expression is obtained for the decay rate of the unmixedness. This expression is very convenient and is recommended for direct practical applications in the modeling and design of plug-flow reactors.