The addition of gyrotactic microbes in the nanoparticles is essential to embellish the thermal efficiency of many systems such as microbial fuel cells, bacteria powered micro-mixers, micro-volumes like microfluidics devices, enzyme biosensor and chip-shaped microdevices like bio-microsystems. Porous media also plays a pivotal role in augmentation of the thermal efficiency. Our approach in the present work is to offer a novel study of bioconvection due to gyrotactic microbes in a nanofluid flow comprising thermal radiation within a porous media over a nonlinear shrinking/stretching surface. The entire coupled system involving nonlinear equations is tackled by means of Successive over Relaxation technique. The impacts of the involved parameters on the flow, motile microbes diffusion rate, mass and heat transfer rates are examined and shown through diagrams and tables. Comparisons with graphical and tabular data are provided and observed to be in a good agreement. Numerical results evidently point out that the motile microbes parameter and the bioconvection Peclet number elevate the motile microorganisms’ density whereas the thermal radiation phenomenon enhances the temperature.

Hybrid nanofluids can provide better physical strength, thermal conductivity, and mechanical resistance in many thermodynamic systems than pure nanofluids. To establish the novel results, using superior types of hybrid nanoparticles like graphene oxide (GO) and iron oxide (Fe ₃ O ₄ ) is the main focus of recent work. This study investigates the innovative thermal and magnetic features of both pure nanofluid GO / engine oil (EO) and hybrid nanofluid GO–Fe ₃ O ₄ / EO under the simultaneous effects of induced as well as applied magnetic field. The chemical reaction phenomenon together with activation energy has also been taken into account. A novel algorithm based on order reduction and finite difference discretization is developed in order to numerically treat the problem. The efficiency of the code is appraised by a numerical comparison which is found to be in a good correlation with the existing results. From the consequences of this study, it is deduced that the reduction in induced magnetic field and fluid’s velocity (in case of either pure or hybrid nanofluid) is associated with the enlarging values of magnetic Prandtl number and induced magnetic field parameter. Further, activation energy is responsible for enhancement in concentration. The hybrid nano-composition of GO–Fe ₃ O ₄ /EO can provide the thermal stability, prevent the corrosion and make the liquid to stay in high temperature.

Taking into account the effect of viscous dissipation in the energy equation, we numerically explore the flow of an incompressible micropolar fluid with heat and mass transfer through a resistive porous medium between plane channel walls. By exploiting a similarity transformation, the governing partial differential equations are transformed into a system of nonlinear coupled ordinary differential equations, which are solved numerically for various problem parameters by means of quasi-linearization. It is found that the effect of viscous dissipation is to increase the heat and mass transfer rate at both the lower and upper walls of the channel.