Abstract
An analytical method for the capillary entry flow of viscoelastic fluid is developed based on the boundary layer approximation to predict the transient behavior of flowrate and development of inflow region starting from at rest. Experiments are carried out for the start-up flow of a viscoelastic polymer solution driven by a constant pressure. The uni-axial elongational viscosity is estimated from the entry pressure loss of terminal steady flows. The inflow region length in steady flow is well predicted by the analytical method with a constant elongational viscosity thus obtained. While, the overshoot and delay of flow rate observed in the experiment are not reproduced at all. This may be attributed to the increase of the elongational viscosity due to strain thickening.
