  Active turbulence in dense active systems is characterized by high vorticity
on a length scale that is large compared to that of individual entities. We
describe the properties of active turbulence as momentum propagation is
screened by frictional damping. As friction is increased, the spacing between
the walls in the nematic director field decreases as a consequence of the more
rapid velocity decays. This leads to, first, a regime with more walls and an
increased number of topological defects, and then to a jammed state in which
the walls deliminate bands of opposing flow, analogous to the shear bands
observed in passive complex fluids.
