Scaling transitions during the thinning of viscous dripping droplets*

The dynamics of filament thinning during the formation of viscous Newtonian drops is studied experimentally and numerically. High speed shadowgraph imaging and sub-pixelar image analysis are used to extract the minimum neck diameter in terms of the time $\tau$ to breakup. Aqueous solutions of glycerol with viscosities ranging from 20 to 360 mPa s are used as the working fluids. In addition, nozzles of different diameters were used to vary the initial dynamic conditions. High resolution numerical simulations were performed to extract the instantaneous Reynolds number to understand the transition between different scaling regimes (presented in detail in a complementary presentation). Our results seem to suggest that, under some conditions, the transition from Potential Flow (PF) to an inertial-viscous (IV) regime is intertwined by a viscous regime (V).