Effects of discharge concentration and convective boundary conditions on unsteady hybrid nanofluid flow in a porous medium

Abstract

This study explores using hybrid nanofluids to improve water quality by enhancing heat transfer and substance decomposition. Nanofluids effectively remove pollutants, optimise heat transfer, control pollution sources, and regulate fluid dynamics, which can lead to efficient pollution management in water systems. Thus, the present research examines the flow of an unsteady hybrid Al2O3–Cu/water nanofluid near the stagnation region in a porous medium, considering the discharge concentration and convective boundary conditions. Governing equations in ordinary differential equations are obtained using similarity transformations. The BVP4C solver in MATLAB is employed to expose dual solutions. The volume fraction of copper φa2, the suction/injection parameter (S), and the unsteadiness parameter (A), collectively contribute to the delay of the boundary layer separation. Increasing the values of φa2,A, and S enhances convective heat transfer. When the sheet shrunk between the range of −16.2 and −13, hybrid nanofluid has higher convective thermal transfer than nanofluid. Moreover, an increment in φa2 and S raises the skin friction coefficients and mass diffusion rates. Stability analysis reveals that the first solution is stable while the second one is unstable.

Keywords

• Hybrid nanofluid
• Boundary layer flow
• Stagnation point flow
• Stretching/shrinking sheet
• Porous medium
• Dual solutions