Active fluids continuously inject energy at the microscopic scale, generating

collective motion and complex flow structures far from equilibrium. Among the

most striking manifestations of this behavior is active turbulence, a chaotic

state that emerges despite the absence of externally imposed forcing and has

become a paradigmatic example of self-organization in active matter.

I will discuss recent progress in understanding active

turbulence using large-scale mesoscopic simulations of active nematic fluids.

The numerical approach provides access to a broad range of length and time

scales, enabling a detailed characterization of the statistical properties of

active turbulent flows and of the mechanisms through which activity transfers

energy across scales. Particular emphasis will be placed on the connection

between active and inertial turbulence. While active turbulence is commonly

viewed as a low-Reynolds-number phenomenon, sufficiently strong active forcing

can trigger hydrodynamic instabilities that lead to regimes where active and

inertial turbulent fluctuations coexist, blurring the traditional distinction

between active and passive turbulent states.

I will further show how topological defects act as the elementary dynamical

objects organizing active turbulent flows. Their morphology, statistics, and

dynamics can be characterized over unprecedented system sizes in both two- and

three-dimensional active nematics, providing insight into the coupling between

orientational order and fluid motion.

Finally, I will present recent results demonstrating that nonreciprocal

interactions fundamentally reshape defect dynamics. By breaking

action--reaction symmetry, nonreciprocity modifies defect-defect interactions

and annihilation pathways, leading to qualitatively new collective behaviors.

These findings reveal new mechanisms through which nonequilibrium interactions

control the organization of active materials and highlight the central role of

topological defects in connecting turbulence, order, and emergent dynamics in

active fluids.