Abstract
In present article, three dimensional peristaltic flow of a Williamson fluid model in rectangular channel has been discussed. The flow is unsteady and caused by propagation of sinusoidal waves due to peristaltic pumping. The equations of motion are derived for constitutive relation of Williamson model and are finally simplified under restrictions of low Reynolds number and long wavelength. The highly nonlinear and nonhomogeneous partial differential equations are solved by using homotopy perturbation method with combination of eigen function expansion method. The expression for pressure rise is found numerically. The final calculations for velocity, pressure gradient, pressure rise and stream functions are narrated graphically.