Motility-Induced Phase Separation in a chaotic environment

"Motility-Induced Phase Separation in a Chaotic Environment". In this project, we attempted to investigate the theoretical description of biological microswimmers and their active dynamics outside of homogeneous habitats. We used Brownian dynamics simulation to mimic bacteria as self-propelled particles (SPP) and direct numerical simulation to generate background cellular flow by solving incompressible Navier-Stokes equation using pseudospectral method. By post-processing the data, we explored the competition between mixing due to cellular flow and motility-induced phase separation. For the first time, we observed that when SPP motility dominates cellular flow, particles exhibit swarming behavior. We also observed that when the velocity of a turbulent flow is comparable to the velocity of SPP, particles accumulate in the region of strain dominating flow. A homogeneous mixture of SPP is another interesting result we acquired by maintaining the velocities of SPP to be much smaller compared to the background fluid which demonstrates that the turbulence is an effective mixer.