  In the present study, we investigated flow structures and properties of
elastic turbulence in straight 2D channel viscoelastic fluid flow and tested
earlier observations. We discovered self-organized cycling process of weakly
unstable coherent structures (CSs) of co-existing streaks and stream-wise
vortices, with the former being destroyed by Kelvin-Helmholtz-like instability
resulting in chaotic structures. The sequence periodically repeats itself
leading to stochastically steady state. This self-sustained process (SSP)
remarkably resembles one investigated theoretically and experimentally for
Newtonian turbulence in straight channel flow. The unexpected new ingredient is
the observation of elastic waves, which finds to be critical for existence of
CSs and SSP generation due to energy pumping from large to smaller scales
preceding sharp power-law decay in elastic turbulence energy spectrum. The
reported finding suggests the universality of CSs in transition to turbulence
via self-organized cycling (SSP) in linearly stable plane shear flows of both
elastic and Newtonian fluids.
