Computer-controlled Two-Roll Mill flow cell for the experimental study of particle and drop dynamics

In this paper, we present for the deformation of a drop under flow, using an experimental device based on the Two-Roll Mill geometry. To study the drop deformation for extended periods of time, the use of this device requires implementation of a non-linear control scheme that has not previously been used. The device and control scheme generate well characterized flow fields, which present a richness of behavior of the drop dynamics that smoothly varies from that observed in simple shear flows, where the vorticity dominates, to those observed in purely Hyperbolic flows. The Two-Roll Mill flow cell allows detailed studies such as the critical capillary number versus the critical viscosities ratio for elongational flows with significant vorticity. As well, the experimental device is able to track the time evolution of the drop shape permitting to study its complex time evolutions. Experiments were performed for sub-millimeter size drops with the determination of the surface tension with high accuracy.