EXAMPLES AND COUNTEREXAMPLES FOR HUYGENS PRINCIPLE IN PREMIXED COMBUSTION

A model involving a scalar reaction-diffusion equation with piecewise linear reaction rates and linear incompressible flow fields is develop ed to study the validity of Huygens principle at large scales in premi xed combustion. This model includes both dependence on the reaction te rm and the velocity field. For plane fronts aligned with the direction of expansive strain and KPP regime, theory predicts strong. violation of Huygens principle chemistry, and this is shown to persist in drama tic fashion throughout the ZFK regime, even at high activation energie s. If the front is aligned with a direction of compressive strain, Huy gens principle yields an excellent approximation with ZFK chemistry. F or a more general rotating strain how with ZFK chemistry, the Huygens principle significantly underpredicts the large scale flame propagatio n velocity in consistent fashion with the example involving expansive strain. For backward reactions or at the boundary of the ZFK regime, H uygens principle is always excellent for any large scale how geometry.