Control of coherent structures in reattaching laminar and turbulent shear layers
Abstract
The development of large-scale vortical structures in reattaching shear layers has been studied experimentally using the flow over a two-dimensional, backward-facing step. Flow visualization has shown the formation and merging of vortical structures, the increasing irregularity of these structures with increasing shear-layer turbulence, and the persistence of the structures far downstream of reattachment. Gentle excitation of the shear layer by an oscillating flap enhances the formation of vortical structures, especially for turbulent separation. LDV measurements show that the excitation significantly intensifies the turbulence activity in the shear layer, but has negligible effect on mean velocity profiles; excitation substantially reduces reattachment length, particularly when separation is turbulent.
- Publication:
-
American Institute of Aeronautics and Astronautics
- Pub Date:
- March 1985
- Bibcode:
- 1985shfc.confQ....R
- Keywords:
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- Laminar Flow;
- Reattached Flow;
- Shear Layers;
- Turbulent Flow;
- Vortices;
- Backward Facing Steps;
- Flow Velocity;
- Flow Visualization;
- Reynolds Stress;
- Two Dimensional Flow;
- Fluid Mechanics and Heat Transfer