Double-diffusive convection in a plane layer with low thermal conductivity boundaries

This study examines double-diffusive convection in a horizontal fluid layer with low thermal conductivity boundaries, where the heat flux is fixed. Using linear stability analysis and nonlinear modeling, the behavior of the system is explored under different thermal and concentration gradients. Two instability modes are identified: monotonous and oscillatory. The monotonous mode, exhibiting longwave patterns, dominates when both gradients contribute to instability. The oscillatory mode occurs when the gradients oppose each other, with stability thresholds dependent on system parameters. Nonlinear modeling confirms the linear theory, showing longwave patterns near the instability threshold and oscillatory behavior when gradients are opposed. These findings offer insights into double-diffusive convection in systems with low thermal conductivity boundaries.