  Our fluid dynamics video shows the response of a layer of viscoelastic fluid
to an array of four-roll mills steadily rotating underneath. When the
relaxation time of the fluid is sufficiently long, the fluid divides into
"cells" with a convex free surface above the site of each roller. This is
reminiscent of the rod-climbing effect. On this relaxation time-scale, the flow
also transitions from being initially Newtonian-like to one where the fluids'
elasticity plays a dynamical role: The fluid cells oscillate with regularity in
position and shape on a timescale much longer than the relaxation time. As the
relaxation time is further increased, the cells become less localized to the
underlying rollers, and their now irregular oscillations reflect the presence
of many frequencies.
