Experiments have been undertaken to characterize the flow field over a delta wing, with an 85 degrees sweep angle, at 12.5 degrees 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.
Development of a three-dimensional free shear layer
Journal of Fluid Mechanics ; 369 ; 49-89
1998
41 Seiten, 36 Quellen
Article (Journal)
English
Low-Dimensional Models of a Temporally Evolving Free Shear Layer
British Library Conference Proceedings | 2006
|Two-dimensional shear-layer entrainment
AIAA | 1986
|