Impact of dilating forcing amplitudes on a peristaltically driven non-Newtonian fluid in an elastic tube: application to swallowing disorders

Abstract

We investigate the flow dynamics within an elastic tube transporting a power-law fluid, where the tube is subject to a specified external forcing in the form of a progressive traveling wave. The oesophagus is cylindrical in shape and exhibits linear elastic properties. The flow is creeping, and the long wavelength and low Reynolds number approximations are employed for a solution. The relationship between the pressure distribution within the oesophagus and the radial variation of the tube characterizes the behavior of the tube. Findings reveal that the elasticity and the variations in the applied dilating forcing amplitude substantially impact pressure resulting from sinusoidal wave forcing. Notably, even a nominal increase in the inward radial force amplitude for dilatant fluid results in significant pressure changes compared with Newtonian fluid. We also observe a notable distinction between time-averaged volume flow rate and velocity in pseudo-plastic and dilatant forms. Our study also identifies that the radial velocity experiences either attenuation or enhancement due to the fluid’s shear thickening and thinning characteristics. Moreover, our research uncovers a novel dimension by highlighting that in shifting from pseudo-plasticity to dilatancy, the fluid requires higher pressure to propel the bolus toward the hiatus. This observation has important implications, suggesting that feeding a more dilatant fluid to patients with pre-diagnosed swallowing disorders, such as sliding hiatus hernia, is not advisable, fearing increased pressure.