title: Ligament Mediated Fragmentation of Viscoelastic Liquids.
abstract: The breakup and atomization of complex fluids can be markedly different than the analogous processes in a simple Newtonian fluid. Atomization of paint, combustion of fuels containing antimisting agents, as well as physiological processes such as sneezing are common examples in which the atomized liquid contains synthetic or biological macromolecules that result in viscoelastic fluid characteristics. Here, we investigate the ligament-mediated fragmentation dynamics of viscoelastic fluids in three different canonical flows. The size distributions measured in each viscoelastic fragmentation process show a systematic broadening from the Newtonian solvent. In each case, the droplet sizes are well described by Gamma distributions which correspond to a fragmentation-coalescence scenario. We use a prototypical axial step strain experiment together with high-speed video imaging to show that this broadening results from the pronounced change in the corrugated shape of viscoelastic ligaments as they separate from the liquid core. These corrugations saturate in amplitude and the measured distributions for viscoelastic liquids in each process are given by a universal probability density function, corresponding to a Gamma distribution with n_{min}=4. The breadth of this size distribution for viscoelastic filaments is shown to be constrained by a geometrical limit which can not be exceeded in ligament-mediated fragmentation phenomena.
authors: Hatsopoulos Microfluids Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Bavand
authors: B
authors: Keshavarz
authors: Axalta Coating Systems, Two Commerce Square, 2001 Market Street, Suite 3600, Philadelphia, Pennsylvania 19103, USA.
authors: Eric C
authors: EC
authors: Houze
authors: Axalta Coating Systems, Two Commerce Square, 2001 Market Street, Suite 3600, Philadelphia, Pennsylvania 19103, USA.
authors: John R
authors: JR
authors: Moore
authors: Axalta Coating Systems, Two Commerce Square, 2001 Market Street, Suite 3600, Philadelphia, Pennsylvania 19103, USA.
authors: Michael R
authors: MR
authors: Koerner
authors: Hatsopoulos Microfluids Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Gareth H
authors: GH
authors: McKinley
mesh_terms: D004548:Elasticity; D008022:Ligaments; D046911:Macromolecular Substances / Q000737:chemistry*; D009330:Nebulizers and Vaporizers; D012212:Rheology; D014783:Viscosity
chemical_list: D046911:Macromolecular Substances