Surface tension in a reactive binary mixture of incompressible fluids

Based on the Cahn-Hilliard free energy, a thermodynamic model for a reactive binary mixture of incompressible and miscible fluids is derived with a distributed form of surface tension. The model describes chemistry, diffusion, viscosity and heat transfer as well as stresses produced by (and at right angles to) concentration gradients. It allows for a rich spectrum of processes and some of these are discussed briefly. Scaling arguments based on experimental data of Abid et al. [1], lead to considerable simplifications. Saffmann-Taylor stability analysis (here extended to interfaces of finite thickness) agrees with the experimental findings of Abid et al. who argued that the buoyant instability of a reaction diffusion front is controlled by a form of surface tension at the front.