Preliminary results are reported from flow visualiztion studies of the separated shear layers on slender delta wings in air at Reynolds numbers from 3000 to 100000 based on chord. The work confirms the existence of a systematic structure in the shear layer paralleling the classic instabilities occurring in other cases. Both quasi two-dimensional instabilities travelling at mean flow velocities and a new form of streamwise instability, believed to result from curvature of the vortex sheet, have been identified. Both instabilities are found to be stabilised by the stretching process towards the centre of the core. For the case studied the interaction between the two instabilities causes the vortex sheet to become turbulent at Reynolds numbers above about 20000 based on local chord. Forced response studies of the vortex sheet have demonstrated the existence of new mechanisms for vortex formation in the shear layer. The results are believed to be relevant to more complex three dimensional shear layers, and have implications for full scale flows on aircraft at high angles of attack.
The three dimensional vortex sheet structure on delta wings
Die dreidimensionale Wirbelschichtstruktur auf Deltafluegeln
1989
16 Seiten, 14 Bilder, 1 Tabelle, 27 Quellen
Conference paper
English
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