Grid Resolution Effects on LES of a Piloted Methane-Air Flame
Cornell University Ithaca United States
Pagination or Media Count:
The grid dependence of LES of a piloted methane-air Sandia D flame is studied on a series of grids with progressively increased resolution reaching about 10 million cells. Chemical compositions, density and temperature fields are modeled based on the evolution of mixture fraction combined with a steady flamelet model. However, to minimize interpolation uncertainties that are routinely introduced by a standard flamelet look-up table procedure, we adopt a simple smooth analytical relationship for specific volume and temperature as functions of mixture fraction. Such an analytical relationship can be easily inferred by approximating a steady flamelet solution by quadratic functions that are known to give a quite accurate representations of the lean mixtures. The simulation results are discussed and compared with available experimental data. In particular, the dependence of LES turbulent statistics on the turbulence resolution length scale is analyzed and tested for the existence of intermediate inertial range asymptotic behavior. For the most part, the statistics converge for the finest grids, but the RMS of the mixture fraction early in the flame shows some residual grid dependence.