Analytical expressions are derived for the velocity vector, the stress components
and the viscosity function in fully developed channel and pipe flow of Phan-Thien–Tanner
(PTT) fluids; both the linearized and the exponential forms of the PTT
equation are considered. The solution shows that the wall shear stress of a PTT
fluid is substantially smaller than the corresponding value for a Newtonian or upper-convected Maxwell fluid, with implications for comparing predicted and measured
values in a non-dimensional form.