Break-up of droplets in a concentrated emulsion flowing through a narrow constriction*

We describe the break-up of droplets in a concentrated emulsion during its flow as a 2D monolayer in a microchannel consisting of a narrow constriction. Analysis of the behavior of over 4000 drops shows that the number of break-ups increases with increasing flow rate, entrance angle to the constriction, and size of the drops. As single drops do not break at the highest flow used, break-ups arise primarily from droplet-droplet interactions. Droplet-droplet interactions are stochastic; they cause fluctuations in the local strain rate and deformation each drop experiences. Analysis of droplet properties at a temporal resolution of 10 microseconds makes it possible to relate drop deformation with break-up probability. Similar to previous studies on single drops, no break-up is observed below certain critical flow rates and droplet deformations. Unlike previous studies, however, not all drops break above the critical values. Instead, the probability of break-up increases with flow rate and the local deformation of the drops.