Understanding Active Turbulence in Fluidized Dry Active Nematics*

Active turbulence within assemblies of self-propelling rods (SPRs) is a fascinating phenomenon characterized by chaotic active flows. To elucidate the fundamental

generation mechanism of active turbulence within 2D dense, dry SPRs, we perform large-scale Brownian dynamics simulations and investigate the cyclic process by

which dry SPRs undergo persistent swarming motions. Moreover, we characterize the coherent system dynamics by tracking the statistical and morphological

properties of disclination defects. We find the natural aggregation of rods leads to the formation of smectic-like rod layers, the deformation of which creates unique polar

structures and impedes the forward motion of +1/2-order defects. In turn, we demonstrate how rod motion near defects gives rise to local-positional orders and the

formation of interlocking polar lanes. Furthermore, we perform instability analysis on a bottom-up active-liquid-crystal model to determine the underlying cause of polar

lane breakup, which effectively leads to the formation of defects. Thus, the perpetual cycle consisting of unstable, smectic-like layers generating topological defects,

which induce smectic-like layers, serves as the origin of chaotic active flows within dense, dry SPRs.