ON THE RESPONSE OF PREMIXED FLAMES TO TIME-DEPENDENT STRETCH AND CURVATURE

In the framework of a constant-density model, we study the linear response of a premixed flame to large scale, but time dependent, curvature and stretch of given strength and frequency. It is analytically suggested that: i) as the frequency of forcing increases above the reciprocal transit time across the flame, the local instantaneous burning speed gets less and less sensitive to hydrodynamical stretch. ii) the influence of differential diffusion of heat and deficient reactant is milder and milder when the high-frequency limit is approached, so that the Lewis-number-effects tend to disappear. The predicted trends are put in perspective with the results of recent measurements on acoustically destabilized flames.