Mixed convective peristaltic transport of hybrid nanofluid in the annular region of eccentric cylinders under lubrication approximation theory

The study investigates mixed-convective peristaltic transport of an Al 2 O 3 –Cu /water hybrid nanofluid in the annular region between eccentric cylinders, a configuration relevant to biomedical devices such as endoscopes and catheters, where heat transfer and flow regulation are critical. Using long-wavelength and low-Reynolds-number approximations, the governing equations were solved analytically through a perturbation method and validated numerically with an error below 0.1%. The results show that fluid temperature increases by up to 18% with higher heat-generation strength and decreases by approximately 12% as eccentricity increases. Velocity rises by nearly 20% with increasing Grashof number due to stronger buoyancy effects. The axial pressure gradient increases markedly by up to 25% with eccentricity and by 15% with inner-cylinder enlargement because of geometric narrowing of the flow passage. The heat-transfer rate (Nusselt number) is enhanced by approximately 30% with larger amplitude ratios and eccentricity, demonstrating stronger thermal transport in the narrowed portions of the eccentric annulus. Likewise, the wall shear stress increases by 18–25% depending on the eccentricity and heat source/sink parameter, indicating higher viscous resistance in constricted regions. Hybrid nanofluid behavior further enhances thermal performance compared with single-nanoparticle nanofluids. The work provides the first combined analysis of mixed convection, heat generation or absorption, and hybrid nanofluid transport in an eccentric annular peristaltic system, extending existing models to more realistic biomedical geometries and offering new insights into thermal–fluid behaviour during endoscope- or catheter-assisted transport.