Couple stresses effect on linear instability and nonlinear stability of convection in a reacting fluid

We study the problem of convective movement of a reacting solute in a viscous incompressible fluid occupying a plane layer and subjected to a couple stresses effects. The thresholds for linear instability are found and compared to those derived by a global nonlinear energy stability analysis. In particular, we analyse the effect of no-slip boundary conditions on the stability and instability of convection. The conditions of no-slip at the boundary with couple stresses effect and non constant coefficients which are analysed for the first time in this article.