Determine the full transition pathway from laminar flow to three-dimensional elastic turbulence in planar channels

Determine the full pathway from laminar flow to three-dimensional elastic turbulence in planar channel flow, including the mechanisms connecting the onset of centre-mode instability and its spanwise modulation to the fully developed turbulent state.

Background

The paper situates elastic turbulence in planar channels as a geometry in which the base flow has straight streamlines and therefore lacks the curvature-driven transition mechanism familiar from curved viscoelastic flows. Previous work has identified a centre-mode instability and subsequent spanwise modulation as likely ingredients in the transition process.

However, the authors explicitly state that the complete route from laminar flow to fully three-dimensional elastic turbulence has not been established. This remains unresolved independently of the paper’s primary focus on elastic turbulence in confined ducts and pipes.

References

In planar channels, although the full pathway from laminar flow to three-dimensional ET remains unresolved, the onset of a centre-mode instability cite{page-dubief-kerswell-2020,khalid-etal-2021,buza-etal-2022}, followed by its modulation in the spanwise direction cite{lellep-linkmann-morozov-2023}, is believed to initiate transition.

— Elastic turbulence in straight confined geometries  (2609.04617 - Rota et al., 4 Sep 2026) in Introduction, paragraph beginning “In planar channels”