Development of a three-dimensional free shear layer
Experiments have been undertaken to characterize the flow field over a delta wing, with an 85° sweep angle, at 12.5° incidence. Application of a laser Doppler anemometer has enabled detailed three-dimensional velocity data to be obtained within the free shear layer, revealing a system of steady co-r...
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Veröffentlicht in: | Journal of fluid mechanics 1998-08, Vol.369, p.49-89 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Experiments have been undertaken to characterize the flow field
over a delta wing, with
an 85° sweep angle, at 12.5° incidence. Application of a laser
Doppler anemometer
has enabled detailed three-dimensional velocity data to be obtained within
the free
shear layer, revealing a system of steady co-rotating vortical structures.
These
sub-vortex structures are associated with low-momentum flow pockets in
the separated
vortex flow. The structures are found to be dependent on local Reynolds
number,
and undergo transition to turbulence. The structural features disappear
as the
sub-vortices are wrapped into the main vortex core. A local three-dimensional
Kelvin–Helmholtz-type instability is suggested for the
formation of these vortical structures
in the free shear layer. This instability has parallels with the cross-flow
instability that
occurs in three-dimensional boundary layers. Velocity data at high Reynolds
numbers
have shown that the sub-vortical structures continue to form, consistent
with flow
visualization results over fighter aircraft at flight Reynolds numbers. |
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ISSN: | 0022-1120 1469-7645 |
DOI: | 10.1017/S0022112098001712 |