Geometry of Reaction Interfaces in Chaotic Flows

The analysis of transport-controlled reactions in chaotic flows provides a physical frame to extend the concept of the intermaterial contact area (ICA)--introduced in the purely kinematic case--to mixing systems with diffusion, where the ICA is identified through the reaction interface between segregated reactants. We show that the dynamics of the ICA undergoes a crossover from kinematics-dominated exponential growth to a persistent oscillatory regime resulting from the intertwined action of advection and diffusion. The scaling of the crossover length versus the Peclet number is analyzed.