Investigating entropy optimization in radiatively peristaltic transport of Casson fluid in the annular region of eccentric cylinders under lubrication hypothesis
Nahed Bahman, Asad Fayyaz, Zaheer Abbas, Muhammad Yousuf Rafiq
Abstract
Non-Newtonian fluids are commonly found in both biological and industrial systems, such as enhanced oil recovery, chemical processing, and biomedical fluid transport. This work investigates the influence of an endoscope on the peristaltic motion of a Casson fluid in an annular region between eccentric cylinders, incorporating entropy generation into the analysis. The outer sinusoidal tube satisfies a no-slip condition, while the uniformly rigid inner tube adheres to slip conditions. The energy equation includes viscous dissipation and thermal radiation effects. Using the long-wavelength and low Reynolds number approximations, closed-form solutions for temperature, streamlines, entropy production, velocity, pressure gradient, and Bejan number are obtained via perturbation methods. Results reveal that fluid velocity increases with the slip parameter (from 0.01 to 0.1) and amplitude ratio (from 0 to 0.4), while it decreases near the inner tube. The temperature decreases by approximately 20 % as the radiation parameter increases from 0.1 to 0.5, but rises with increasing Brinkman number (from 1 to 3), indicating enhanced viscous heating. Entropy generation increases by 35 % with rising Brinkman number, while the Bejan number decreases accordingly, highlighting dominant irreversibilities due to viscous dissipation. These findings have implications for endoscopic procedures, where pressure gradients and temperature regulation are critical, especially during catheter insertion.