TURBULENT PREMIXED COMBUSTION - FURTHER DISCUSSIONS ON THE SCALES OF FLUCTUATIONS

The prediction of turbulent combustion is classically performed by numerical integration of "modeled" equations. For each existing approach, a crucial quantity is a time scale for the destruction of temperature (or concentration) fluctuations. Usually, this time scale is simply taken as proportional to the corresponding time scale for velocity fluctuations, but the question of the influence of the reaction on this scale arises, and has already been discussed. We discuss here this point in the particular case of wrinkled premixed flames. Algebraic closure formulas, as well as closures based on the so-called ε{lunate}y equation, or on the equation for the flame surface by unit of volume of Marble and Broadwell, are proposed and discussed. It is found, in particular, that in the case of wrinkled flames with infinite Damköhler and Reynolds numbers the reaction does not play any direct role on the time scale. © 1990.