Non-linear evolution of thermodiffusively unstable lean premixed hydrogn flames

The characteristic patterns of thermodiffusively unstable lean premixed hydrogen flames are studied in several large-scale simulations conducting a parameter variation with respect to the thermal expansion ratio of the flame. This enables a systematic separation of the influence of the thermodiffusive and Darrieus-Landau instabilities on the flame front’s evolution. A detailed chemical mechanism is employed and the variation of the thermal expansion ratio is obtained by a modification of the equation of state. For all simulations, the flame front corrugation possesses two characteristic length scales. In particular, flames without thermal expansion also feature both length scales, suggesting that both length scales originate from the thermodiffusive instability. Additionally, the size of the largest characteristic length scale is found to increase with the thermal expansion ratio.