Collective Behavior of Swimmers in Fluids at Intermediate Reynolds Numbers

Emergent active matter behavior is observed in both biological and artificial systems. So far, most active-matter systems that include many-body hydrodynamic interactions have focused on small length scales in Stokes flows. However, a whole region of parameter space, that is mesoscale active matter, i.e. active matter of inertial particles in fluids at intermediate Reynolds numbers (Re), remains largely unexplored. We use the immersed boundary method to model the collective behavior of model swimmers at intermediate Re. We will talk about our results on the hydrodynamic interactions between swimmers, and we show how the onset of swimming, fluid flows and forces between them varies as a function of Re and how it differs from Stokes flows. We discuss next steps for how to build a statistical framework of inertial swimmers.