Observation of Hele-Shaw flow of a viscoelastic fluid

The Hele-Shaw cell is used to examine the effect of elasticity on the flow patterns of two-dimensional potential flow. Flows around a circular cylinder and two abruptly converging-diverging channels with different throat lengths are tested for a Newtonian fluid (water) and a PAA-solution. When the flow rate is higher than a certain value, the streamlines of the PAA-solution near the upstream stagnation point of the circular cylinder are shifted upstream separating from the cylinder surface, while streamlines approach to the cylinder surface near the downstream stagnation point. In the flow through the abruptly converging-diverging channels at shear rates higher than a critical value, a pair of vortices is formed on both sides of upstream abruptly converging section, while the streamlines attach to the wall at the downstream abruptly diverging section.