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ISSN オンライン: 2642-0554

STABILIZATION OF SUBCRITICAL BYPASS TRANSITION IN THE LEADING-EDGE BOUNDARY LAYER BY SUCTION

Michael O. John
Institute of Fluid Dynamics ETH Zurich 8092 Zurich, Switzerland

Dominik Obrist
Institute of Fluid Dynamics, ETH Zurich Sonneggstr. 3, 8092 Zurich, Switzerland

Leonhard Kleiser
Institute of Fluid Dynamics ETH Zurich ETH Zentrum, CH-8092 Zurich, Switzerland

要約

This work investigates the subcritical transition in the swept Hiemenz boundary layer (SHBL) by means of direct numerical simulations (DNS). A combination of a steady and a time-dependent disturbance leads to spatial bypass transition. The primary disturbance consists of steady co-rotating vortices, leading to streaks. The secondary, time-dependent disturbance interacts with the streaks and instability and breakdown may occur. The instability is strictly of secondary nature and only occurs for a certain band of secondary disturbance frequencies.
The influence of uniform suction across the wall on this bypass transition is investigated. Analogous to results from linear stability theory, also the secondary stability is enhanced by suction. Depending on the Reynolds number and the suction strength, the unstable disturbances are shown to be either localized structures, convected along the streamlines, or global structures, covering broad regions in the downstream direction.