MHD nanofluid bioconvection due to gyrotactic microorganisms over a convectively heat stretching sheet

• Investigate nanofluids containing motile gyrotactic microorganisms.
• Buongiorno model is employed with convective boundary condition.
• The Nusselt numbers decrease with increasing magnetic field.
• The Sherwood numbers decrease with increasing magnetic field.
• The density number decreases with increasing magnetic field.

MHD laminar boundary layer flow with heat and mass transfer of an electrically conducting water-based nanofluid containing gyrotactic microorganisms along a convectively heated stretching sheet is investigated numerically. The governing equations are reduced to non-linear ordinary differential equations using Oberbeck–Boussinesq approximation and similarity transformations. The effects of the governing parameters on the dimensionless quantities like velocity, temperature, nanoparticle concentration, density of motile microorganisms, local Nusselt, and local Sherwood numbers for both nanoparticles and motile microorganism density are explored. It is found that the dimensionless velocity decreases with increasing buoyancy ratio and bioconvection Rayleigh number and the dimensionless temperature at the surface increases with an increase in the convective parameter, whereas it decreases with increasing buoyancy ratios.