Numerical solution of peristaltic transport of an Oldroyd 8-constant fluid in a circular cylindrical tube

Abstract

The present paper is concerned with the peristaltic flow of a non-Newtonian fluid in circular cylindrical tube. Long wavelength and low Reynolds number approximations are adopted in the problem definition. The non-Newtonian behaviour of the fluid is characterized by the constitutive equation of an Oldroyd 8-constant fluid. The governing nonlinear equation and boundary conditions are solved numerically by a suitable finite-difference method with an iterative scheme. It is seen that shear-thinning and shear-thickening phenomena can be explained through the chosen fluid model. The interaction of shear-thinning and shear-thickening effects with peristaltic motion is studied in detail with particular focus on the basic features of peristalsis such as flow characteristics, pumping characteristics, and trapping. It is found that pressure rise per wavelength against which peristalsis has to work as a positive displacement pump decreases in going from shear-thickening to shear-thinning fluids. Moreover, for strong shear-thinning fluids trapping does not appear. However, a trapped bolus occurs for a weak shear-thinning fluid and its size increases as the fluid is changing from shear thinning towards weak shear thickening. For strong shear-thickening fluids such increase in the size and circulation of bolus stops.