... thresholds for perturbations. The instability and nonlinear thresholds are computed using two high-accuracy Chebyshev collocation methods (standard and boundary-fitted). Findings Brinkman viscous diffusion and higher-order thermal/solutal diffusion act predominantly as stabilising mechanisms...

... associated with the theory is found. The numerical method based on the Chebyshev collocation technique is used to analyze linear instability thresholds by solving the eigenvalue system. Findings The numerical results clearly identify the regions of instability, as well as the zones where either...