| CNRS-NSF Workshop Transport and Mixing of reactive and non reactive flows in the Atmospheric Boundary Layer Paris, July 4, 2001 |
| Angelo Vulpiani Department of Physics, University of Rome "La Sapienza", Italy Front propagation in reacting passive scalars advected by laminar flows The problem of front propagation in a stirred medium is addressed for flow with cellular patterns. As a consequence of stirring, the effective velocity of the front is enhanced with respect to the non-stirred case. For fast advection the front advances with a velocity proportional to U^{1/4}, where U is the stirring intensity, whereas for slow advection the front speed is proportional to U^{3/4}. The macroscopic dynamics of the concentration field is described in terms of an effective reaction-diffusion equation with renormalized parameters. The theoretical predictions for the effective front velocity are confirmed by direct numerical simulations. |