Influence of thermal radiation on mixed convection heat and mass transfer stagnation-point flow in nanofluids over stretching/shrinking sheet in a porous medium with chemical reaction

• Concentration increases with Schmidt number for stretching and shrinking sheets.
• Copper–water nanofluid has higher skin-friction coefficient and mass transfer rate.
• Sherwood number decreases for higher values of nanoparticle volume fraction.
• Cu–water has lower heat transfer rate compared to Al2O3–water and TiO2–water.
• Skin-friction increases with porous parameter and nanoparticle volume fraction.

We have investigated the mixed convection boundary layer flow of nanofluids on a stagnation-point flow over a permeable stretching/shrinking sheet subject to thermal radiation, heat source/sink, viscous dissipation and chemical reaction by using numerical method. Three types of nanofluids namely copper–water, alumina–water, titanium dioxide–water were considered in the present study. The governing boundary layer equations are transformed into a system of nonlinear ordinary differential equations by using similarity transformation which are then solved numerically using fifth-order Runge–Kutta–Fehlberg method with shooting technique. The effects of various physical parameters are analyzed and discussed in graphical and tabular form. The effects of some physical parameters such as mixed convection parameter, radiation parameter, Schimdt number, porous parameter, Eckert number, chemical reaction parameter are analyzed on velocity, temperature and concentration profiles as well as on skin-friction coefficient, local Nusselt number and Sherwood number. It is found that copper–water exhibits higher mass transfer rates compared to alumina–water and titanium dioxide–water nanofluids for stretching and shrinking sheets.