K.D. Visser, M. del Carmen Ferrero Ferrero, R.C. Nelson

Qualitative and quantitative aspects of the flow structures associated with the shear layer and rollup process of delta wing vortices are examined in an effort to understand the nature of the shear layer sub-structures. Both periodic and stationary structures have been observed in the shear layer separating from the sharp leading edge of a highly swept wing. The former emanate in a close to parallel direction with the leading edge while the latter appear to leave the edge at more normal angles and then wind around the core vortex structure. It is proposed that the appearance of these helical striations, observed in wind tunnel smoke flow visualization and measurement studies, flight vehicle visualization studies, and recent computational studies, are a result of cross-flow instabilities in the boundary layer on the underside, or windward side, of the lifting surface. This instability, as observed on swept wings, rotating disks, and rotating cylinders, generates co-rotating vortex structures, in contrast to centrifugal instabilities, such as that caused by curvature, which generate counter-rotating vortices. At lower Reynolds numbers these structures remain distinct as they are convected in the shear layer and wrap around the primary vortex, while at higher Reynolds numbers it is speculated that the structures smear the visualization smoke before becoming entrained into the flow, although they can still be discerned with flow field measurements. Additional hypotheses, including Kelvin-Helmholtz, transversal, and longitudinal instabilities, are discussed.

CEAS/KATnet Conference on Key Aerodynamic Technologies, Bremen, 2005

Conference Paper

englisch

21,0 x 29,7 cm, 15 Seiten

DGLR-Bericht, 2005, 2005-07, CEAS/KATnet Conference on Key Aerodynamic Technologies - Proceedings; S.1-15; 2005; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

in getr. Zählung;

aerodynamics

Bibliothek

2005