Coarsening Dynamics of Binary Liquids Under Active Rotation
Open Access
- Author:
- Sabrina, Syeda
- Graduate Program:
- Chemical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 04, 2014
- Committee Members:
- Kyle Jeffrey Magnuson Bishop, Thesis Advisor/Co-Advisor
- Keywords:
- Active matter
Coarsening Dynamics
Nonequilibrium
Cahn-Hilliard
Phase-separation - Abstract:
- Active matter comprised of many self-driven units (e.g. colloidal swimmers) exhibits emergent collective behaviors such as clustering, swarming and segregating depending on the nature of the local energy input, the nature of the energy dissipation, and the interactions between the individual units. In a recent microscopic model of actively rotating spinners, it was shown that a binary mixture of particles under active rotation phase separate into domains of like-rotating particles in 2-dimensions (2D). The size of these domains R, grows in time as R ~ t1/3 under “weak” rotation with frictional drag as the dominant damping force. This result is in agreement with the classic diffusion-controlled demixing of passive binary liquid mixtures without active rotation. Other more exotic types of coarsening are anticipated in this nonequilibrium system as a function of the strength of active rotation as compared to that of frictional damping and viscous damping in the system. Here we develop a continuum 2D model of phase separation in binary liquids under active rotation and systematically explore its different dynamical regimes. Our model combines the convective Cahn-Hilliard equation governing the local composition field and the Navier-Stokes equation with active rotation and frictional damping governing the velocity field. Besides recovering diffusion-controlled coarsening under conditions of “weak” rotation, our model predicts a variety of new behaviors such as active coarsening and the emergence of “vortex-doublets”. These numerical results are reproduced and explained by scaling arguments that outline the different dynamical regimes and elucidate the diverse behaviors therein.