Original Contribution

Rheologica Acta

, Volume 48, Issue 6, pp 611-624

First online:

Droplet formation in quickly stretched liquid filaments

  • David F. JamesAffiliated withDepartment of Mechanical and Industrial Engineering, University of Toronto Email author 
  • , Mohammad PouranAffiliated withDepartment of Mechanical and Industrial Engineering, University of TorontoFluor Enterprises Inc.

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Abstract

Film splitting necessarily occurs in roll coating and unwanted droplets can occur at high machine speeds when the resulting filaments break up. To study this ‘misting’ problem, an apparatus was designed and built to simulate filament fluid mechanics. The device creates a filament by elongating a liquid bridge and stretches the filament at a high and constant rate of acceleration to mimic coating machine kinematics. Filament breakup was observed using a high-speed video camera and the images were analyzed to yield droplet size and number. With Newtonian fluids, a single droplet formed at Ohnesorge (Oh) numbers less than 0.1 and more and smaller droplets were produced at Oh numbers above 0.1. Associative polymer solutions, prepared as weakly elastic fluids to represent industrial coatings, produced even more and smaller droplets, but only for Ohnesorge numbers in the range of 0.01 to 0.1.

Keywords

Filament breakup Quick stretching Misting Droplets Elasticity Uniaxial extension