Continuum kinetic modeling of active turbulence

Active fluids are continuously driven out of equilibrium due to the stresses generated by their microscopic constituents. These non-equilibrium dynamics, often called active turbulence, are characterized by jets, vortices, and topological defects that can span scales orders of magnitude larger than those of the constitutive particles. Many phenomenological active fluid models have been found to reproduce these dynamics, but such models typically lack a clear energetic structure. In this talk, we discuss active turbulence in a continuum kinetic model of a suspension of extensile particles -- an example of an active nematic fluid. We derive coarse-grained equations, based on the Bingham closure, that allow for efficient simulations at high particle activity while retaining the energetic structure of the kinetic theory. Simulations reveal a nonlinear length scale selection in the active force that drives self-similar dynamics at large scales, and we analytically characterize these dynamics through a balance of entropy production and dissipation that is uniquely accessible from the kinetic description.