SI movie 2

Comparison of steady and unsteady flow behavior in the $l_s = W_0$ 1-D pore array. (a-b) Fluid pathline imaging for the weakly shear-thinning, highly elastic 300 ppm HPAM, Gl-Aq solution in pore body 16 showing (a) 2D steady flow (Wi = 1.8, De = 0.14) and (b) 3D, time-dependent, multistable (Wi = 26, De = 3) flow behavior. Flow is from left to right. (c-d) Fluid pathline imaging for the highly shear-thinning, highly elastic 4500 ppm HPAM, Gl-Aq solution showing (c) 2D steady flow (Wi = 10, De = 0.3) and (d) 3D unsteady, multistable (Wi = 34, De = 1) flow behavior. Unsteady flow behavior is visualized by crossing pathlines and fluctuations in the eddy sizes. Both solutions exhibit multistability in the time-dependent flow state, as described in the main text; thus, the presence of moderate shear-thinning does not abrogate multistability. The movies shown correspond to an ``eddy-dominated' pore over the imaging window. 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.