The study of the rheological properties of polymeric solutions in steady flow using a slit rheometer

A functional dependence of exit pressure on wall shear stress was developed for viscoelastic fluids. In the limit of low Reynolds number, a quadratic dependence of exit pressure was postulated that resulted in a simple expression for the primary normal stress difference in terms of exit pressure N sub 1 = 3 p supp (HL). Data on four theologically different fluids confirmed the quadratic dependence on p supp (HL) on tau sub W at low shears. At high Reynolds numbers where inertial terms are dominant, N sub 1 was estimated using momentum equations. For highly elastic fluids and fluids whose inertia was too low to produce a jet with measurable thrust, slit flow also permitted estimation of N sub 1. Thus, the use of a slit rheometer offers potential for evaluating normal stresses over a much wider range of shear rates than previously thought.