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Stability of toroidal droplets inside yield stress materials
E Pairam1, H Le1, A Fernández-Nieves1
1School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30339-0430, USA.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 13, 2014
Summary
The stability of toroidal droplets in yield stress materials is governed by their shape. Elasticity can prevent breakup or self-coalescence, with specific radius conditions observed.
Area of Science:
- Rheology and Soft Matter Physics
- Fluid Dynamics of Complex Fluids
Background:
- Toroidal droplets in viscous liquids exhibit instabilities like breakup or self-coalescence, dependent on their slenderness.
- Yield stress materials possess a threshold stress below which they behave as a solid, influencing droplet dynamics.
Purpose of the Study:
- To investigate the stability of toroidal droplets confined within a yield stress material.
- To determine the influence of the outer medium's elasticity on toroidal droplet instabilities.
- To compare the conditions required to prevent breakup versus self-coalescence.
Main Methods:
- Theoretical analysis of toroidal droplet dynamics within a yield stress fluid.
- Modeling the interplay between surface tension, yield stress, and elasticity.
- Comparison of deformation mechanics for different instability pathways.
Main Results:
- The slenderness of the toroidal droplet dictates its stability, similar to viscous liquids.
- The elasticity of the yield stress material can suppress breakup and self-coalescence.
- A larger tube radius is required to prevent breakup than to prevent self-coalescence.
Conclusions:
- A simple model balancing surface tension and yield stress accurately predicts toroidal droplet stability.
- The distinct deformation requirements for preventing breakup and self-coalescence explain the observed radius differences.
- Elasticity plays a crucial role in stabilizing toroidal structures in yield stress fluids.
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