SIMULATION OF FRONT PROPAGATION AT LARGE NONDIMENSIONAL FLOW DISTURBANCE INTENSITIES

Numerical modeling of propagating fronts in non-uniform two-dimensional flow fields is performed in order to simulate the effect of such flows on premixed flame fronts. In particular, the influence of the flow disturbance intensity (u') on the mean front propagation rate (S-T) is examined. A second-order numerical technique is employed that combines the level set (G-equation) formulation to describe the self-propagation of the front and a multidimensional upwind technique to describe the convection of the front by the flow field. In this way the effect of the non-dimensional disturbance intensity (u'/S-L) on the non-dimensional propagation rate (S-T/S-L) at values of u'/S-L >> 1 is computed. The dependence of the laminar propagation speed (S-L) on the flame stretch (including both the front curvature and the velocity strain effects) is incorporated in this formulation. We focus on front propagation in simulated Taylor-Couette flows in the ''Taylor vortex'' regime and the results are found to compare favorably with recent experiments on the propagation of isothermal chemical fronts in this flow. The formation of ''islands'' of reactants is observed and its relation to front propagation rates is discussed.