Trailing-edge jet control of leading-edge vortices of a delta wing

Abstract

The effect of using a trailing-edge jet to control the leading-edge vortices of a delta wing is investigated experimentally in a water towing tank facility. The Reynolds number, based on the freestream velocity and the root chord, is 9.8 X 103. Both static and dynamic (pitching-up) conditions are tested. For the dynamic cases, the wing is pitched from 10- to 45-deg angle of attack with pitch rates varied from 0.043 to 0.26. From the dye flow visualization, it is shown that a downward vectored trailing-edge jet can significantly delay the vortex breakdown on a delta wing. Strong asymmetric breakdown of the leading-edge vortices can be induced by arranging the vectored jet in an asymmetric configuration. Transient pitching motion delays the onset of the vortex breakdown. The initial delay is independent of the pitch rate. Also, the use of jet control is found to be effective for the dynamic cases. During the initial pitching-up period, the use of jet control has a dominant influence on the propagation of the vortex breakdown. In general, with jet control, the propagation of the vortex breakdown slows down. From instantaneous particle image velocimetry measurements, a quasiperiodic variation of the leading-edge vorticity field is detected before the vortex breakdown. This variation appears to relate to the strong interaction between the separating shear layer, the secondary vortex, and the primary vortex. Along the vortex axis, the velocity distribution changes from a jet-type profile to a wake-type profile, signifying the onset of vortex breakdown.