COMPUTATIONS OF STEADY-STATE AND TRANSIENT PREMIXED TURBULENT FLAMES USING PDF METHODS

Premixed propagating turbulent flames are modeled using a one-point, s ingle time, joint velocity-composition probability density function (p df) closure. The pdf evolution equation is solved using a Monte Carlo method. The unclosed terms in the pdf equation are modeled using a mod ified version of the binomial Langevin model for scalar mixing of Vali no and Dopazo, and the Haworth and Pope (HP) and Lagrangian Speziale-S arkar-Gatski (LSSG) models for the viscous dissipation of velocity and the fluctuating pressure gradient. The source terms for the presumed one-step chemical reaction are extracted from the rate of fuel consump tion in laminar premixed hydrocarbon flames, computed using a detailed chemical kinetic mechanism. Steady-state and transient solutions are obtained for planar turbulent methane-air and propane-air flames. The transient solution method features a coupling with a Finite Volume (FV ) code to obtain the mean pressure field. The results are compared wit h the burning velocity measurements of Abdel-Gayed et al. and with vel ocity measurements obtained in freely propagating propane-air flames b y Videto and Santavicca. The effects of different upstream turbulence fields, chemical source terms (different fuels and strained/unstrained laminar flames) and the influence of the velocity statistics models ( HP and LSSG) are assessed.