CALCULATIONS OF SUBSONIC AND SUPERSONIC TURBULENT REACTING MIXING LAYERS USING PROBABILITY DENSITY-FUNCTION METHODS

A particle method applying the probability density function (PDF) appr oach to turbulent compressible reacting flows is presented. The method is applied to low and high Mach number reacting plane mixing layers. Good agreement is obtained between the model calculations and the avai lable experimental data. The PDF equation is solved using a Lagrangian Monte Carlo method. To represent the effects of compressibility on th e flow, the velocity PDF formulation is extended to include thermodyna mic variables such as the pressure and the internal energy. Full closu re of the joint PDF transport equation is made possible in this way wi thout coupling to a finite-difference-type solver. The stochastic diff erential equations (SDE) that model the evolution of Lagrangian partic le properties are based on existing models for the effects of compress ibility on turbulence. The chemistry studied is the fast hydrogen-fluo rine reaction. For the low Mach number runs, low heat release calculat ions are performed with equivalence ratios different from one. Heat re lease is then increased to study the effect of chemical reaction on th e mixing layer growth rate. The subsonic results are compared with exp erimental data, and good overall agreement is obtained. The calculatio ns are then performed at a higher Mach number, and the results are com pared with the subsonic results. Our purpose in this paper is not to a ssess the performances of existing models for compressible or reacting flows. It is rather to present a new approach extending the domain of applicability of PDF methods to high-speed combustion. (C) 1998 Ameri can Institute of Physics. [S1070-6631(98)00302-X].