Time resolved flow-field measurements of a turbulent mixing layer over a rectangular cavity |
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Authors: | Shiyao Bian James F Driscoll Brian R Elbing Steven L Ceccio |
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Affiliation: | (1) Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA;(2) Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109, USA;(3) Applied Research Laboratory, Pennsylvania State University, State College, PA 16804, USA |
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Abstract: | High Reynolds number, low Mach number, turbulent shear flow past a rectangular, shallow cavity has been experimentally investigated
with the use of dual-camera cinematographic particle image velocimetry (CPIV). The CPIV had a 3 kHz sampling rate, which was
sufficient to monitor the time evolution of large-scale vortices as they formed, evolved downstream and impinged on the downstream
cavity wall. The time-averaged flow properties (velocity and vorticity fields, streamwise velocity profiles and momentum and
vorticity thickness) were in agreement with previous cavity flow studies under similar operating conditions. The time-resolved
results show that the separated shear layer quickly rolled-up and formed eddies immediately downstream of the separation point.
The vortices convect downstream at approximately half the free-stream speed. Vorticity strength intermittency as the structures
approach the downstream edge suggests an increase in the three-dimensionality of the flow. Time-resolved correlations reveal
that the in-plane coherence of the vortices decays within 2–3 structure diameters, and quasi-periodic flow features are present
with a vortex passage frequency of ~1 kHz. The power spectra of the vertical velocity fluctuations within the shear layer
revealed a peak at a non-dimensional frequency corresponding to that predicted using linear, inviscid instability theory. |
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