The results of the derived analytical expression for the volumetric flow rate (i.e. Eq. 19 with n = 1, k = µ and ∂p/∂z = ∇P ) were compared to the results of this formula (i.e. Eq. 27) and they were identical. A sample of these comparisons is given in Figure . 3. Circular power law: the volumetric flow rate for the flow of power law fluids through a circular tube of radius R is given by (see ):