Flames with Realistic Thermal Expansion in a Time-Dependent Turbulent Flow

The propagation velocity of turbulent premixed flames with real thermal expansion in a time-dependent external flow is studied for an infinitely thin flame front and for flames of small but finite thickness. It is shown that the influence of temporal pulsations is usually small and can be neglected for reasonable values of the pulsation frequency. The role of pulsations is even smaller for realistic thermal expansion in comparison with the artificial case of zero thermal expansion studied previously. The results obtained indicate that the Taylor hypothesis of “ stationary” turbulence is a good approximation for turbulent flames. The role of pulsations is substantial only if the integral turbulent length scale is close to the cut-off wavelength of the Darrieus-Landau instability. In this particular case, temporal pulsations can be important for explaining recent experiments on turbulent burning.