Chemically driven convection

We present the linear and nonlinear analysis of a horizontal layer of initially quiescent, simple dissociating Navier-Stokes fluid (2A?A2) in the Boussinesq approximation neglecting Dufour effect terms. To facilitate the analysis of the far from equilibrium states, the mathematically simplest free surface boundary conditions have been chosen at which either and/or the extent of dissociation or temperature are fixed. We find that in this system two classes of instability can develop. The first brought on by increasing an already adverse density gradient is similar to the conventional Bénard instability. The second class of instability is novel, and we designate them as chemical instabilities. These instabilities are not correlated to the values of the adverse density gradients and do not appear in a purely quiescent fluid. We are thus dealing with true chemically driven convection.