Atomization of smooth sheets of non-Newtonian liquids

The focus of the present work is to study the fragmentation of liquid sheets formed from shear-thinning gels with a specific focus on ligament-droplet transition in a smooth sheet regime. Water-based gels using Carbopol as a gellant are used as simulant liquids. Two identical liquid jets are impinged to forma liquid sheet, and visualization experiments are conducted using a wide range of Weber numbers. High-speed imaging reveals two primary regimes of sheet breakup: smooth sheet regime and flapping sheet regime. These regimes further show various sub-regimes with distinctive features depending upon the Weber number and the gellant concentration. We choose a set of operating conditions pertaining to the smooth sheet regime in each gel sample for further investigation. Destabilization of a curved rim bounding the sheet, under the action of Rayleigh-Plateau instability, centrifuges the ligaments anchored to the rim. These are extremely smooth ligaments resulting from viscous stretching. Combining the observations of the present study with the theory of rim-ligament-droplet transition (Bremond and Villermaux, 2006), it is shown that the droplet statistics are relatively narrow as compared to Newtonian liquids and may be described by a single parameter gamma distribution.