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

In the framework of a constant-density model, we study the linear resp onse of a premixed flame to large scale, but time dependent, curvature and stretch of given strength and frequency. It is analytically sugge sted that: i) as the frequency of forcing increases above the reciproc al transit time across the flame, the local instantaneous burning spee d gets less and less sensitive to hydrodynamical stretch. ii) the infl uence of differential diffusion of heat and deficient reactant is mild er 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.