(474b) Structure and Dynamics of Swimming Microorganisms in External Fluid Flows

Suspensions of swimming microorganisms are one example of active colloidal systems. The activity keeps the system always far from equilibrium and leads to unique structure and dynamics. Many researchers have studied how interactions between active colloids alter the collective structures formed. Researchers have also examined interactions with confining walls that leads to a non-uniform density of cells (they concentrate near the walls). In this talk we will discuss computer simulations of these systems in external fluid flows. The simulations use the Brownian dynamics methodology including hydrodynamic interactions of the organisms with the walls.

We find that the external flow dramatically alters the distribution of the organisms across the channel. We examine the role of the strength of the external flow and the flow type (Couette versus Poiseuille) which alters the cell distribution. The change in distribution can be understood using the orientation distribution of the cells, and how the flow alters that distribution. We will also discuss the dynamics of the cells, and how those dynamics could impact other processes such as biofilm formation.