Theoretical analysis of energy transport in magnetised bioconvective micropolar nanofluid flow over a stretching sheet: a Cattaneo-Christov model

Abstract In this paper, we examine the magneto-hydrodynamic (MHD) stagnation-point flow of an electrically conducting micropolar nanofluid over a stretching sheet in a porous medium. Mathematically, the model integrates the combined effects of non-Fourier Cattaneo-Christov thermal flux, Arrhenius activation energy with binary chemical reaction, Joule heating, thermal radiation, and bioconvection due to gyrotactic microorganisms in a novel manner. The problem is governed by nonlinear boundary layer partial differential equations which are transformed into a system of coupled ordinary differential equations using similarity transformations and solved numerically using the MATLAB solver bvp5c with the addition of a firing technique. The computational results show that the mainline velocity increases with an increase in the stretching ratio parameter whilst the micro-rotation of the particle is decreased. Cattaneo- Christov thermal relaxation decreases the heat penetration. The thermal boundary layer thickness decreases with Cattaneo- Christov thermal relaxation. Thermal radiation, viscous dissipation and Joule heating increase the temperature dispersion considerably. The increase in activation energy reduces the consumption of species and improves the concentration field of nanoparticles. The bioconvective Lewis and Peclet numbers lower the density of motile microorganisms in the boundary layer. Quantitatively, the skin-friction coefficient and couple stress are enhanced with micropolar and magnetic parameters, the local Nusselt number is significantly enhanced by thermal radiation and relaxation, and the Sherwood number is enhanced with chemical reaction strength. These discoveries provide essential physical standards for the design of sophisticated microfluidic bio-devices, microbial fuel cells, polymer coating processes and efficient geothermal energy systems.