Unsteady double-diffusive convective flow of an Oldroyd-B hybrid nanofluid in a porous medium with cross-diffusion effects

This research focuses on convection driven by a thermal gradient and a concentration gradient in an Oldroyd-B hybrid nanofluid saturated by a highly permeable layer with cross-diffusion effects. The Buongiorno model is implemented with the diversity of thermophoresis and Brownian diffusion. Using linear stability theory, an analytical expression for thermal Rayleigh number is obtained at the onset of binary liquid convection. For the nonlinear analysis, the governing PDEs are altered into ODEs by making use of similarity transformations. The rate of heat and mass transfer are calculated with the help of the built-in function NDSolve in computational tool MATHEMATICA 12.0. The numerical results are offered for the base fluid as ethylene glycol with hybrid copper and silver nanoparticles. The graphical illustrations are described to understand the impact of all the emerging parameters on the onset of convective phenomenon. Hybrid nanofluid is found to be more stable in comparison with single particle nanofluid. As far as technological applications are concerned, mono nanofluid could be replaced by hybrid nanofluid and this can be stated as a novelty of the article. We have observed that the heat and mass transfer profile is boosted up for increasing viscoelastic parameters i.e. stress relaxation and strain retardation parameters, solutal Rayleigh number and Prandtl number. In addition, the heat transfer displays an increasing nature toward the higher amounts of nanoparticle volume fraction.