Frozen fronts in cellular flows

We present experiments on the behavior of reaction fronts in ordered and disordered cellular flows with imposed winds. Fronts in a chain of alternating vortices are found to freeze (pin to the separatrix) for a wide range of imposed winds that grows nonlinearly with the characteristic strength of the underlying vorticity. Experiments in spatially-disordered flows demonstrate that freezing of fronts is common to cellular flows; furthermore, it is not dependent on boundary conditions. We therefore anticipate similar pinning in a wide range of cellular flows and front-producing systems.