Dandan Chen, Kenneth W. Desmond, Eric R. Weeks
We experimentally study the shear flow of oil-in-water emulsion droplets in a thin sample chamber with a hopper shape. In this thin chamber, the droplets are formed into quasi-2D pancakes, somewhat analogous to soft photoelastic disks. We can track the droplets' motions to measure strain in our sample, and their deformed outlines lets us infer the stresses within the sample. As the sample flows through the hopper we observe large stress fluctuations, similar to what has been seen in other flows of complex fluids. We show a direct relationship between T1 events (where four droplets rearrange) and the macroscopic stress fluctuations. A T1 event influences the stress up to 3 droplet diameters away.
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http://arxiv.org/abs/1105.3099
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