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TURBULENCE TRANSITION IN THE ASYMPTOTIC SUCTION BOUNDARY LAYER

Tobias Kreilos
Fachbereich Physik Philipps-Universitat Marburg Renthof 6, D-35032 Marburg, Germany

Taras Khapko
Linne FLOW Centre KTH Mechanics Osquars Backe 18, SE-100 44 Stockholm, Sweden

Tobias M. Schneider
Max Planck Institute for Dynamics and Self-Organization Am Fassberg 17, D-37077 Gottingen, Germany

Gregor Veble
Pipistrel d.o.o. Ajdovina Gorika c. 50a, SI-5270 Ajdovina, Slovenia

Yohann Duguet
LIMSI-CNRS UPR 3251, F-91403 Orsay, France

Phillipp Schlatter
Linne FLOW Centre and Swedish e-Science Research Centre (SeRC) KTH Mechanics, Royal Institute of Technology SE-100 44 Stockholm, Sweden

Dan S. Henningson
Linne FLOW Centre and Swedish e-Science Research Centre (SeRC) KTH Mechanics, Royal Institute of Technology SE-100 44 Stockholm, Sweden

Bruno Eckhardt
Fachbereich Physik, Philipps-Universitat Marburg Renthof 6, D-35032 Marburg, Germany

Abstract

We study the transition to turbulence in the asymptotic suction boundary layer (ASBL) by direct numerical simulation. Tracking the motion of trajectories intermediate between laminar and turbulent states we can identify the invariant object inside the laminar-turbulent boundary, the edge state. In small domains, the flow behaves like a travelling wave over short time intervals. On longer times one notes that the energy shows strong bursts at regular time intervals. During the bursts the streak structure is lost, but it reforms, translated in the spanwise direction by half the domain size. Varying the suction velocity allows to embed the flow into a family of flows that interpolate between plane Couette flow and the ASBL. Near the plane Couette limit, the edge state is a travelling wave. Increasing the suction, the travelling wave and a symmetry-related copy of it undergo a saddle-node infinite-period (SNIPER) bifurcation that leads to bursting and discrete-symmetry shifts. In wider domains, the structures localize in the spanwise direction, and the flow in the active region is similar to the one in small domains. There are still periodic bursts at which the flow structures are shifted, but the shift-distance is no longer connected to a discrete symmetry of the flow geometry. Two different states are found by edge tracking techniques, one where structures are shifted to the same side at every burst and one where they are alternatingly shifted to the left and to the right.