Unconfined Droplet Breakup around Cylindrical Obstacles

We study the breakup of quasi-2D droplets in microfluidics around a single cylindrical obstacle, where droplets may either break up against the obstacle or slide laterally around it, a unique situation from more typical studies where droplets move through constricted hallways. We can predict which behavior of the droplet we will see from the fluid properties of the system and the properties of the droplet-obstacle collision at the first moment of contact between the two. These same parameters predict the size of the daughter droplets produced when the droplets will break up, helping us predict an output distribution of sizes. This single obstacle breakup is half of the larger question of how droplets change size when being flowed through a porous media. The other half is droplet coalescence, which we also observe. These droplets break up around many obstacles and coalesce with each other, changing into some media-dependent size distribution, applicable in geophysical flows, PFAS cleanup and pharmaceutical manufacturing.