MHD analysis of couple stress nanofluid through a tapered non-uniform channel with porous media and slip-convective boundary effects

The current research addresses the peristaltic transport mechanism that propels fluid through a conduit through rhythmic contraction and relaxation of the conduit walls, a phenomenon evident in numerous biological systems, including the gastrointestinal tract. Motivated by applications in nano-pharmacological drug delivery and thermo-biomagnetic therapy, a mathematical and computational analysis of radiative heat transfer in peristaltic pumping of a magnetohydrodynamic (MHD) couple stress nanofluid through a tapered asymmetric passage, with the influences of a porous medium and wall slip, is presented. Buongiorno's two-component nanoscale model is deployed and the Stokes couple stress non-Newtonian model utilized. Physically the porous medium is modelled with a drag force formulation and simulates the presence of obstructions and deposits in the gastric tract and blood vessels. The governing equations for the couple stress nanofluid are reduced by employing the long-wavelength approximation and the low Reynolds number condition, both standard approaches in fluid dynamics research. Analytical solutions are derived for axial velocity, temperature profile, nanoparticle concentration, stream function, and pressure gradient, providing a comprehensive understanding of the flow dynamics. Furthermore, numerical integration methods are utilized to calculate the average pressure increase (ΔP) and the heat transfer coefficient (Z). The impact of critical parameters namely the Hartmann number (M), Brownian motion parameter ( N b ), thermophoresis parameter ( N t ), Prandtl number (Pr), slip parameter (L) and radiation parameter (R n ) on fluid dynamics is examined through comprehensive graphical representations. The findings indicate that peristaltic pumping efficiency is superior in a uniform channel relative to a non-uniform channel, underscoring the influence of channel geometry on flow performance. Moreover, the synergistic effects of thermophoresis and Brownian motion result in a substantial elevation of fluid temperature, enhancing thermal energy transfer throughout the system. Increasing wall slip parameter diminishes the friction between the fluid and the channel walls, facilitating smoother fluid flow and decreasing thermal resistance. Stronger radiative heat flux promotes energy absorption in the system, resulting in accelerated fluid cooling at the boundary of the conduit (channel). Increasing non-uniformity parameter associated with asymmetry (m) leads to a diminished nanoparticle concentration. Increasing Brownian motion nanoscale parameter elevates nanoparticle concentrations. A strong modification is also computed with thermophoretic nanoscale parameter. Heat transfer coefficient displays oscillatory behavior attributable to the contraction and expansion of the channel walls. The complete flow zone is categorized into four quadrants (peristaltic pumping zone, increased flow zone, free pumping zone and retrograde pumping zone) based on the pressure difference (Δ P ) and time average of the flux over one period of the wave (Θ), each indicating a distinct flow behavior. Increasing Hartmann magnetic number augments peristaltic pumping. An increase in Grashof number (Gr) i.e. thermal buoyancy parameter correlates with enhanced pumping throughout all four quadrants. This study offers significant insights into enhancing peristaltic transport processes in industrial, medicinal, and environmental contexts, especially concerning MHD nanofluids inside intricate geometries featuring porous media and slip circumstances.