Experimental investigation of non-Newtonian droplet collisions
the role of extensional viscosity
Giulia Finotello (Eindhoven University of Technology)
Shauvik De (Eindhoven University of Technology)
Jeroen C.R. Vrouwenvelder (Eindhoven University of Technology)
Johan T. Padding (TU Delft - Intensified Reaction and Separation Systems)
Kay A. Buist (Eindhoven University of Technology)
Alfred Jongsma (Tetra Pak CPS)
Fredrik Innings (Tetra Pak CPS)
J. A.M. Kuipers (Eindhoven University of Technology)
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Abstract
We investigate the collision behaviour of a shear thinning non-Newtonian fluid xanthan, by binary droplet collision experiments. Droplet collisions of non-Newtonian fluids are more complex than their Newtonian counterpart as the viscosity no longer remains constant during the collision process. Despite the complex collision dynamics, we are able to present a complete regime map based on non-dimensional Weber (We) number and impact parameter (B). We compare the collision outcomes of xanthan, glycerol and a milk concentrate at similar impact conditions. These experiments reveal very rich and complex collision morphologies for shear thinning xanthan solution, strikingly different from Newtonian droplet collisions. Unlike glycerol and milk, xanthan collisions show no reflexive separation even at very high We number. Instead of breakup, we observe disc-like shapes with an oscillating behaviour of the colliding droplets. A detailed analysis reveals that this outcome is related to increased viscous energy dissipation and extensional effects.
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