On periodically excited turbulent mixing layer created downstream of a plane Chevron partition

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

The flow in a turbulent mixing layer resulting from the merger of two parallel, different velocity streams, created downstream of a 'Chevron'-shaped jagged partition was simulated numerically on the basis of experiments published in 2007. A small flap that was hinged at the trailing edge of the partition could oscillate at a prescribed frequency, and induce regular oscillations in the flow. The latter regulated the large eddy structure that was amenable to phase-locked data acquisition revealing the large spanwise vortices that were generated by Kelvin-Helmholtz instability and streamwise vortices that were triggered by the chevron and were enhanced by a secondary instability in the flow. These, being locked in phase, were mapped by using particle image velocimetry. Numerical simulation of the equations of motion was then carried out in order to reveal the most unstable mechanisms leading to the generation of the streamwise vortical structure. The simulation started by assuming the flow to be two-dimensional (2D) and allowing the large spanwise eddies to develop temporally. At a prescribed time (or the state of development of the large spanwise rolls) the 2D computation was frozen and 3D simulation initiated. The latter exhibited typical evolution of translative instability, which bent the large spanwise structures and stretched some of them to create streamwise vorticity. Bulging of the spanwise eddies was also observed, but the bulging instability is a slower process than the bending one. The results of the simulations compare well to experiments and provide some understanding of this complex interaction.

Original languageEnglish (US)
Title of host publicationPhysica Scripta T
VolumeT132
DOIs
StatePublished - 2008
EventInternational Conference 'Turbulent Mixing and Beyond' - Trieste, Italy
Duration: Aug 18 2007Aug 26 2007

Other

OtherInternational Conference 'Turbulent Mixing and Beyond'
CountryItaly
CityTrieste
Period8/18/078/26/07

Fingerprint

turbulent mixing
partitions
vortices
bulging
simulation
Kelvin-Helmholtz instability
trailing edges
particle image velocimetry
vorticity
data acquisition
equations of motion
oscillations
interactions

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

On periodically excited turbulent mixing layer created downstream of a plane Chevron partition. / Kit, E.; Wygnanski, Israel J.

Physica Scripta T. Vol. T132 2008. 014008.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Kit, E & Wygnanski, IJ 2008, On periodically excited turbulent mixing layer created downstream of a plane Chevron partition. in Physica Scripta T. vol. T132, 014008, International Conference 'Turbulent Mixing and Beyond', Trieste, Italy, 8/18/07. https://doi.org/10.1088/0031-8949/2008/T132/014008
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