SI Video 3

Comparison of multistable and non-multistable flow behavior above the onset of unsteady, time-dependent flow for polymer solutions in the $l_s = W_0$ 1-D pore array. (a-c) 3D, time-dependent flow exhibiting multistability for the moderately shear-thinning, highly elastic 900 ppm HPAM, Gl-Aq-DMSO solution in three consecutive pore bodies. Pore bodies 15 and 16 appear eddy-dominated over the imaging window, while pore body 17 transitions between eddy-dominated and eddy-free states. Flow is from left to right. (d-f) 3D, time-dependent flow showing no multistability for the highly shear-thinning, moderately elastic 3700 ppm HPAM, Aq solution. The unstable flow is observed qualitatively by crossing pathlines in the bulk of the pore body and fluctuations of the small corner eddies. However, all pore bodies exhibit the same unsteady flow behavior at the same imposed flow rate, showing a lack of multistability. Imaging is recorded sequentially in adjacent pores, producing a time offset of 2 minutes from pore-to-pore. Fluid pathlines are generated using a moving average of the fluorescence intensity of tracer particles over 30 successive frames. Scale bar is $500 \: \upmu$m. Videos play at 15x real time.