Abstract
The flow of a viscoelastic fluid in porous channels with expanding or contracting walls is investigated. Using a similar transformation, the governing equations are reduced to a nonlinear fifth-order differential equation. The homotopy analysis method is employed to obtain the expression for velocity fields. The analytical solutions are influenced by the permeation Reynolds number Re, the wall expansion ratio α and viscoelastic parameter ω. Graphs are sketched and the effects of some values of parameters, especially the expansion ratio, on the velocity fields are discussed in detail.