Experimental and numerical analysis of droplet deformation in a complex flow generated by a rotor–stator device

The deformation behaviour of single drops suspended in a second immiscible liquid undergoing a complex laminar flow is analysed both experimentally and numerically. The flow is generated in a channel formed by two rotating concentric cylinders with teethed walls as a model for extruding flow. The transient drop deformation and position in the device is captured by a twin-camera system in which one camera captures the drop deformation and the other camera captures the position of the drop. Results from an experiment consist of the transient drop deformation and the particle track of the drop. In our data analysis we define a geometry-based apparent shear rate which we compare to time-averaged drop deformations. Results indicate that for small deformations the relation between the time-averaged drop deformation and time-averaged apparent shear rate can be described by Taylor's small deformation theory.Furthermore we have used the particle track data obtained from a number of experiments to numerically calculate the local flow experienced by the drop. The numerically calculated local flow is then used as input to a computational algorithm for simulating the transient drop deformation. Comparison between numerical calculations of the drop deformation and experimental results generally agree well although calculations predict a somewhat higher deformation than experimentally observed.