EXPLICIT ALGEBRAIC SCALAR-FLUX MODELS FOR TURBULENT REACTING FLOWS

Explicit algebraic scalar-flux models that are valid for three-dimensi onal turbulent flows are derived from a hierarchy of second-order mome nt closures. The mathematical procedure is based on the Cayley-Hamilto n theorem and is an extension of the scheme developed by Taulbee. Seve ral closures for the pressure-scalar gradient correlations are conside red and explicit algebraic relations are provided for the velocity-sca lar correlations in both nonreacting and reacting flows. In the latter , the role of the Damkohler number is exhibited in isothermal turbulen t flows with nonpremixed reactants. The relationship between these clo sures and traditional models based on the linear gradient-diffusion ap proximation is theoretically established. The results of model predict ions are assessed by comparison with available laboratory data in turb ulent jet flows.