Autocatalytic reaction front in a pulsative periodic flow

Abstract

Autocatalytic reaction fronts between reacted and unreacted species may propagate as solitary waves, namely at a constant front velocity and with a stationary concentration profile, resulting from a balance between molecular diffusion and chemical reaction. A velocity field in the supporting medium may affect the propagation of such fronts through different phenomena: convection, diffusion enhancement, front shape changes... We report here on an experimental study and lattice BGK numerical simulations of the effect of an oscillating flow on the autocatalytic reaction between iodate and arsenous acid in a Hele-Shaw cell. In the low frequency range covered by the experiments, the front behavior is controlled by the flow across the gap and can be reproduced with 2D numerical simulations. An analytical solution is also derived under the condition of a weak flow velocity, and is found to be in reasonable agreement with our data.