Lateral migration of viscoelastic droplets in a viscoelastic confined flow: role of discrete phase viscoelasticity.
basic_science · Level V
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- Record sourced from PubMed, PMID 31675049.
- Also identified by DOI 10.1039/c9sm01469a.
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Abstract
The cross-stream motion of viscoelastic droplets in viscoelastic fluids has received little attention since the classical study of migration of drops in a second order fluid. In this work, going beyond the existing classical theory, we experimentally elucidate the effect of drop-to-medium viscosity ratio k and elasticity ratio ξ on wall and center migration of viscoelastic droplets in a Poiseuille flow of a viscoelastic medium (PVP) at low Reynolds numbers (Re ≪ 1). We observed a contrasting migration behavior of Newtonian and viscoelastic droplets having the same viscosity ratios and propose the presence of a lift force F<sub>VD</sub> due to the viscoelasticity of the droplet phase. We use analytical scaling and empirical modelling to show that the force F<sub>VD</sub> scales with a prefactor that depends upon the Weissenberg number Wi<sub>D</sub> and drop-to-medium viscosity ratio k and elasticity ratio ξ. Further, we utilize the proposed force for sorting of viscoelastic and Newtonian droplets.