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VOLUMETRIC INVESTIGATION OF VORTEX PAIRING IN A WALL JET IN AIR

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Vortex pairing is a key mechanism for energy transfer of small to large coherent vortices. This paper describes the three dimensional pairing process under predefined conditions on the basis of 3D Least-Squares-Matching (LSM). Therefore, the bottom edge of a nozzle outlet is aligned horizontally to a wall. The nozzles’ system pressure (and thereby the Reynolds number) as well as the camera position downstream the wake can be varied. Shear layer roll-up is observed close to the nozzle forming typical roller structures, which undergo streamwise instabilities further downstream. With increasing Reynolds number, the rollers start to interact with each other; the instabilities trigger localized vortex pairing. The triggering process is documented in the results which provide insight into the three-dimensional vortex pairing dynamics.

Author(s):

David Hess    
TU-Freiberg; Department of Mechanics and Fluid Dynamics,
Germany

Christoph Skupsch    
TU-Freiberg; Department of Mechanics and Fluid Dynamics,
Germany

Jens Kitzhofer    
Dantec Dynamics A/S
Denmark

Christoph Brücker    
TU-Freiberg; Department of Mechanics and Fluid Dynamics,
Germany