Complexity of localised coherent structures in a boundary-layer flow

TL;DR

This paper investigates the complex, localized coherent structures in a boundary-layer flow with suction, revealing multistability and bifurcations leading to chaos, and shows that the edge dynamics are low-dimensional and non-extensive.

Contribution

It provides a detailed numerical analysis of localized edge states in a boundary-layer flow with suction, highlighting their complex bifurcation structure and low-dimensional dynamics.

Findings

Localized states exhibit multistability and complex bifurcations.

Edge dynamics are essentially low-dimensional.

Transitions from periodic to chaotic regimes are observed.

Abstract

We study numerically transitional coherent structures in a boundary-layer flow with homogeneous suction at the wall (the so-called asymptotic suction boundary layer ASBL). The dynamics restricted to the laminar-turbulent separatrix is investigated in a spanwise-extended domain that allows for robust localisation of all edge states. We work at fixed Reynolds number and study the edge states as a function of the streamwise period. We demonstrate the complex spatio-temporal dynamics of these localised states, which exhibits multistability and undergoes complex bifurcations leading from periodic to chaotic regimes. It is argued that in all regimes the dynamics restricted to the edge is essentially low-dimensional and non-extensive.