NUMERICAL-SIMULATION OF FLAME DISTURBANCE GROWTH INDUCED BY A PRESSURE-GRADIENT

As a premixed methane-air flame is accelerated by a pressure wave, spikes penetrating into the burnt gas appear on the flame front, eventually leading to the formation of a turbulent flame. A model of a two-dimensional, inviscid flow in which the flame is considered to be a source of volume and vorticity is shown to develop spikelike features. The source of volume models the thermal expansion occurring inside the flame. The vorticity inside the flame is generated by the pressure gradient across the flame front. In the course of the computations, Fourier transform techniques were used to eliminate small-scale disturbances and hence simulate the stabilizing effects of thermodiffusive factors. A simulation was carried out with, as the initial flame configuration, a flame shape taken from experiment. The simulation resulted in the growth of a spike into the burnt gas that is in good agreement with the experimental observation, at least in the first stages of the simulation.