ON HYDRODYNAMIC INSTABILITY OF STRETCHED FLAMES

The recent result on the diffusive instability of a planar premixed ga s flame sustained in the stagnation-point flow are carried over on the hydrodynamic (Darrieus-Landau) instability. Similar to the former cas e the planar flame of the infinite aspect length-scale is unconditiona lly stable for any flow induced stretch however small. Yet in finite g eometries occuring in numerical and laboratory experiments the flame m ay well become unstable provided the imposed stretch is weak enough. I t is argued that the effect may be related to the formation of a non-s teady multiple cusp structure often observed in large-scale flames.