Single droplet dynamics under oscillatory extensional flow based on eccentric cylinder flow

The dynamics of a single droplet suffered by an oscillatory extensional flow has been investigated by many researchers. However, generating an oscillatory extensional flow in experiments is difficult, thus, in these research, the behaviors of the droplet were studied by simulations. In this work, we proposed a method for observing the dynamics of dispersed phase in oscillatory extensional flow experimentally based on eccentric cylinder flow and used this method to systematically investigate the dynamics of a single droplet under the oscillatory extensional flow. The uniformity of the flow field around the particle was discussed through simulation. The effect of the oscillation period, amplitude, and viscosity ratio on the deformation and orientation of droplet has been systematically investigated. The experimental results are compared with theoretical predictions of the phenomenological model by Maffettone and Minale. In addition, we discussed the behavior of droplets with different initial shapes in the oscillatory extensional flow. For all experiments studied here, good agreement was found between model predictions and experimental data. This work provides, for the first time, an experimental reference data set about droplet dynamics under oscillatory extensional flow, which can be used to guide the droplet modeling in future.