COMPUTATION OF TURBULENT REACTIVE FLOWS - 1ST-PRINCIPLES MACRO MICROMIXING MODELS USING PROBABILITY DENSITY-FUNCTION METHODS

Reactive flows encountered in the chemical industry commonly involve turbulent fluid motion, complex chemical kinetics, and nontrivial reactor geometries. When applied to these flows, traditional computational fluid dynamics approaches based on solving a turbulence model coupled with chemical balance equations often prove inadequate due to their inability (or to the high cost needed) to resolve the microscales of the concentration fields. In this work, an alternative computational methodology based on probability-density-function (PDF) methods is introduced. In the PDF approach, both macro- and micromixing are treated explicitly using first-principles physical models. The crucial unclosed term in the PDF description of reactive flows is that associated with subgrid-scale micromixing. Here, results found using the Fokker-Planck closure for passive scalar mixing and for a second-order reaction in homogeneouS turbulence are presented.