  Simulations of elastoinertial turbulence (EIT) of a polymer solution at low
Reynolds number are shown to display localized polymer stretch fluctuations.
These are very similar to structures arising from linear stability
(Tollmien-Schlichting (TS) modes) and resolvent analyses: i.e., critical-layer
structures localized where the mean fluid velocity equals the wavespeed.
Computation of self-sustained nonlinear TS waves reveals that the critical
layer exhibits stagnation points that generate sheets of large polymer stretch.
These kinematics may be the genesis of similar structures in EIT.
