Transitional turbulence in active nematic channel flow: phase space geometry and exact coherent structures

Confined active nematics exhibit rich dynamical behavior, including spontaneous flows, periodic defect dynamics, and chaotic `active turbulence'. Here, we study these phenomena using the framework of Exact Coherent Structures, which has been successful in characterizing the routes to high Reynolds number turbulence of passive fluids. Exact Coherent Structures are stationary, periodic, quasiperiodic, or traveling wave solutions of the hydrodynamic equations that, together with their invariant manifolds, serve as an organizing template of the dynamics. Here, we apply this framework to active nematic channel flows exhibiting transitional turbulence, obtaining a reduced order—but fully nonlinear—description of the turbulent dynamics. We then discuss how this description can motivate control strategies for suppressing or delaying the onset of turbulence in the transitional regime.