  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
quasi-2D in shape. The sample is at an area fraction above jamming and forced
to flow with a constant flux rate. Stresses applied to a droplet from its
neighbors deform the droplet outline, and this deformation is quantified to
provide an ad hoc measure of the stress. As the sample flows through the hopper
we see large fluctuations of the stress, similar in character to what has been
seen in other flows of complex fluids. Periods of time with large decreases in
stress are correlated with bursts of elementary rearrangement events ("T1
events" where four droplets rearrange). More specifically, we see a local
relationship between these observations: a T1 event decreases the inter-droplet
forces up to 3 droplet diameters away from the event. This directly connects
microscopic structural changes to macroscopic fluctuations, and confirms
theoretical pictures of local rearrangements influencing nearby regions. These
local rearrangements are an important means of reducing and redistributing
stresses within a flowing material.
