Abstract
In the present paper, we discuss the peristaltic flow of a Newtonian fluid in vertical porous annulus. The viscosity of the fluid is treated as a variable. The inner tube is at rest while the outer tube has a sinusoidal wave traveling down its motion. For the sake of simplicity, long wavelength and low Reynold number assumptions are taken into account. The perturbation solution for velocity field and temperature profile are presented in terms of sigma(2) (porosity parameter) and G(m) (Grashof number). Numerical results that show the physical effects and the pertinent features are investigated at the end of the paper.