Front Propagation Rates in Randomly Stirred Media

Experimental data on the rate of advance $(s)$ of a propagating front in a stirred medium was obtained using reaction-diffusion fronts in aqueous solution and two types of hydrodynamic flows. Two distinct propagation modes are observed depending on a Damk\"ohler number (Da) indicating the ratio of a chemical rate to a hydrodynamic strain rate. For low Da, values of s are consistent with a Huygens propagation model employing renormalization group analysis. For high Da, values of s are consistent with a classical model. These results are compared to traditional experiments using premixed combustible gases.