Heat and mass transfer of non-Newtonian nanofluids in assisting/reverse flow over shrinking/stretching surfaces in porous media

This study investigates the radiative, non-isothermal heat, and mass transfer in the stagnation point flow of Maxwell, micropolar, and Williamson nanofluids over a shrinking or stretching sheet embedded in a porous medium driven by buoyancy forces. The effects of suction or injection at the boundary, thermal radiation, and internal heat generation or absorption are considered in assisting or reversing flows. Applying similarity transformations reduces the governing boundary layer equations to nonlinear ordinary differential equations, which are solved numerically using an appropriate method via MAPLE 24. The impacts of key physical parameters are presented and compared through graphs. The numerical results demonstrate that micropolar nanofluids enhance heat and mass transfer but exhibit higher skin friction. The Nusselt number is 12–18% higher for micropolar nanofluids than Maxwell and Williamson nanofluids due to microrotation effects. In comparison, suction enhances heat transfer by up to 20% by reducing the thermal boundary layer thickness. Similarly, mass transfer analysis shows that the Sherwood number is up to 25% higher for shrinking sheets due to a steeper concentration gradient, and suction enhances mass transfer by approximately 18%. In comparison, injection reduces it by 10–15%.