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44948-AC9
Double Diffusive Instabilites of Reaction Diffusion Fronts

Abdelfattah M. Zebib, Rutgers, the State University of New Jersey

Dynamic instabilities driven by thermal and compositional density gradients across two miscible-fluid interfaces are important in many geophysical and environmental applications. In several situations it is chemical reactions that are at the origin of these gradients, for example, in oil biodegradation, underground carbon storage, radioactive decomposition, geochemical transformations, and combustion processes. Our research project aims at understanding these instabilities in porous media and continuous fluids. We have done a reasonably complete study of autocatalytic chemical fronts in Hele-Shaw cells and porous media and classified the instabilities in the four arrangements where thermal and concentration effects are stabilizing and/or destabilizing. It is remarkable that in the quadrant where both effects are stabilizing, and where the classical double diffusive studies show unconditional convective stability, we uncovered a new convective instability driven by chemistry and double diffusion.

We are now considering continuous fluids described by the Navier-Stokes equations and have made substantial progress with the linear theory. We expect to finish the linear theory and conduct nonlinear simulations in 07-08.

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