Active suspension of self-rotating particles

Suspensions of self-propelled particles, such as bacteria, have received considerable attention. Recently there has been increased interest in suspensions of self-rotating particles, such as Quincke rotors driven by electric fields and ferromagnetic colloids in magnetic fields. While the individual particles are governed by relatively simple dynamics, the interaction of the particles can result in complex collective dynamics. Experiments show phase separation, macroscopic directed motion, and structure formation (e.g. vortices). Modeling these systems as discrete particles at the micro-scale (Yeo et al, PRL(2015)) is computationally expensive and limits the study of the rotors collective dynamics. We develop a continuum model based on the one for fluids with internal rotation (Rosensweig, J. Chem. Phys. (2004)). The model allows us to study properties of the fluid and the existence of active turbulence caused by the rotors. To study the effect of confinement, we include phase parameter to restrict the rotors inside a region with a defined diffuse interface. We then can study the interaction between the rotors and the interface for both a fixed and deformable interface