Surface Rotation of Liquid Droplets Under a Simple Shear Flow: Experimental Observations in 3D

The study of droplets sheared by a simple flow, that is, the characterization of the dynamics followed by a small liquid drop submerged in another continuous fluid phase when the latter is sheared, is an interesting field of research, because the implication in basic research and applications. This work studies an interesting feature of the sheared drop: its surface rotation around an axis normal to the flow plane, induced by the flow. Direct observations with a 3D experimental set-up enable the experimental characterization of such rotation in qualitative and quantitative terms, as a function of the strength of the applied flow and for different drop liquid viscosities. As stated in literature, it should be possible to determine the interfacial tension of the liquid-liquid interface from the drop rotation, but efforts in this sense indicate that this method arises in considerably high deviations respect to the measured value.