Computational investigation of MHD stagnation point flow of Eyring-Powell nanofluid with microorganisms over a cylinder under Cattaneo-Christov heat and mass flux.

This study investigates magnetohydrodynamic stagnation point flow with non-Fourier heat and mass transfer in an Eyring-Powell nanofluid containing gyrotactic microorganisms over an inclined porous cylindrical surface. The model simultaneously incorporates the Buongiorno nanofluid formulation, nonlinear thermal radiation, Arrhenius activation energy, Brownian motion, thermophoresis, Darcy porous medium resistance, and dual Cattaneo-Christov heat and mass flux model, thereby establishing a unified framework for analysing coupled momentum, thermal, concentration, and bioconvective transport phenomena. The transformed coupled nonlinear governing equations are reduced to a system of ordinary differential equations using suitable similarity transformations and solved numerically using the MATLAB bvp4c solver. The results reveal that the Eyring-Powell parameter suppresses the velocity field by increasing nonlinear rheological resistance, whereas thermal radiation, Brownian motion, thermophoresis, and curvature enhance thermal energy transport. In contrast, thermal relaxation weakens heat transfer by delaying thermal propagation, while Arrhenius activation energy suppresses the chemical reaction rate, thereby preserving nanoparticle concentration. Furthermore, increasing the bioconvection Peclet number reduces the motile microorganism distribution because advective transport dominates microorganism diffusion. Quantitatively, the skin-friction coefficient increases from 0.75 to 0.84, corresponding to an enhancement of about 12% with increasing chemical reaction parameter and decreasing activation energy. Moreover, the local Nusselt number rises from 1.4 to 3.6 (about 157%) with increasing radiation parameter and decreasing heat generation parameter, whereas the local Sherwood number increases from 0.782 to 0.802 (about 2.6%) with increasing chemical reaction parameter and decreasing activation energy. These findings provide new insights into the coupled transport mechanisms governing reactive bioconvective non-Newtonian nanofluids and offer useful guidance for the design and optimization of porous thermal management systems, catalytic reactors, geothermal energy technologies, and microorganism-assisted transport processes.