Eur. Phys. J. E (2014) 37: 32
https://doi.org/10.1140/epje/i2014-14032-3

Regular Article

Complexity of localised coherent structures in a boundary-layer flow

¹ KTH Mechanics, Linné FLOW Centre, Osquars Backe 18, SE-100 44, Stockholm, Sweden
² Swedish e-Science Research Centre (SeRC), Stockholm, Sweden
³ LIMSI-CNRS, UPR 3251, F-91403, Orsay Cedex, France
⁴ Fachbereich Physik, Philipps-Universität Marburg, Renthof 6, D-35032, Marburg, Germany
⁵ Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, D-37077, Göttingen, Germany
⁶ J.M. Burgerscentrum, Delft University of Technology, Mekelweg 2, NL-2628 CD, Delft, The Netherlands

^* e-mail: taras@mech.kth.se

Received: 31 July 2013
Revised: 27 September 2013
Accepted: 17 October 2013
Published online: 28 April 2014

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.