Item

Abstract

Suspensions of active agents with nematic interactions exhibit complex spatiotemporal dynamics such as
mesoscale turbulence. Since the Reynolds number of microscopic flows is very small on the scale of
individual agents, inertial effects are typically excluded in continuum theories of active nematic turbulence.
Whether active stresses can collectively excite inertial flows is currently unclear. To address this question,
we investigate a two-dimensional continuum theory for active nematic turbulence. In particular, we
compare mesoscale turbulence with and without the effects of advective inertia. We find that inertial effects
can influence the flow already close to the onset of the turbulent state and, moreover, give rise to large-scale
fluid motion for strong active driving. A detailed analysis of the kinetic energy budget reveals an energy
transfer to large scales mediated by inertial advection. While this transfer is small in comparison to energy
injection and dissipation, its effects accumulate over time. The inclusion of friction, which is typically
present in experiments, can compensate for this effect. The findings suggest that the inclusion of inertia and
friction may be necessary for dynamically consistent theories of active nematic turbulence.