Localised edge states nucleate turbulence in extended plane Couette cells

TL;DR

This paper investigates how localized edge states serve as critical nuclei that initiate turbulence in large plane Couette flow domains, revealing their structure and role in the transition process.

Contribution

It identifies and characterizes localized invariant structures in extended plane Couette flow, demonstrating their role as nucleation sites for turbulence.

Findings

Localized states exist in spanwise and downstream directions.

These states act as critical nuclei for turbulence transition.

Invariant structures are identified in large domains.

Abstract

We study the turbulence transition of plane Couette flow in large domains where localised perturbations are observed to generate growing turbulent spots. Extending previous studies on the boundary between laminar and turbulent dynamics we determine invariant structures intermediate between laminar and turbulent flow. In wide but short domains we find states that are localised in spanwise direction, and in wide and long domains the states are also localised in downstream direction. These localised states act as critical nuclei for the transition to turbulence in spatially extended domains.