ON SELF-ACCELERATION OF OUTWARD PROPAGATING WRINKLED FLAMES

Numerical simulations of hydrodynamically unstable outward propagating premixed flames are presented. In a qualitative agreement with many experimental observations it is shown that the expanding wrinkled flames enjoy an appreciable acceleration. The morphology of expanding wrinkled flames appears to be essentially different from that occurring in non-expanding flames. In the latter case short-wavelength corrugations merge forming a single cusp, whose scale is controlled by the overall size of the system. In expanding flames the tendency to merge is balanced by the overall stretch. As a result the flame interface appears to be more or less uniformly wrinkled. In contrast to hydrodynamically unstable flames, expanding flames, subject exclusively to the effect of diffusive instability, do not indicate any disposition towards acceleration.