Low Speed Straked Delta Wing
Abstract
Straked wings have become common features of advanced fighter-type aircraft. The strakes are designed to generate vortices from their highly swept leading edges, which stabilize the flow over the wing and provide additional lift up to high angles of amuck In this way the strakes contribute much to a high maneuverability. The vortex lift capability of straked wings has been extensively explored and experimental data concerning aerodynamic loading are available for various platforms and Mach numbers. The knowledge of unsteady loading on straked wings is less developed, both in the cases where the loading is due to wing oscillations - as required for aircraft stability and flutter analysis - and in cases where fluctuations in the flow are induced by vortex burst (or vortex breakdown) - as required for stall and buffet predictions. Some physical aspects of the unsteady vortex flow are described briefly below. Vortices are shed from the leading edges of the strake and the wing. The sharp leading edges generate vortex sheets, even at low incidence, which roll up spirally into the strake vortices and flow downstream over the wing. The vortices induce strong lateral velocities at the strake and wing upper surface, giving rise to suction peaks at the position of the vortex cores. When the lateral velocities are large enough, secondary flow separations occur, leading to secondary vortices spiraling opposite to the primary vortices At moderate incidences vortex sheets start to develop from the wing leading edges, starting at the kinks. At higher incidences vortex burst or vortex breakdown occurs, intimacy for the wing vortices, followed by the strake vortices. An important consequence of vortex burst is that the corresponding suction peaks become weaker and that the vortices lose their ability to produce additional lift. A normal behavior of vortex burst is that it will move upstream when the incidence increases.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2000
- Accession Number
- ADP010727
Entities
People
- Evert G. Geurts
Organizations
- National Aerospace Laboratory