Vortex control technique for the attenuation of fin buffet

Abstract

The application of tangential leading edge blowing (TLEB) to reduce levels of single-fin buffeting has been studied. The tests were performed at the University of Bath 2.1 x 1.5 m wind tunnel, using two cropped 60deg delta wings. To measure the unsteady pressures on the fin surface, a rigid fin instrumented with miniature differential pressure transducers was used. A flexible fin of similar planform and size was used to measure the buffeting response. Steady-state static pressure data and laser light sheet flow visualization were employed to aid interpretation of the vortical flow over the wings, and hence, identify the causes of the buffeting. The profiles of the unsteady pressures and the buffeting response were found to match each other very closely. It was observed that symmetric leading-edge blowing modified the leading-edge vortices by reducing the effective angle of attack of the vortex. Blowing at a constant rate shifted the buffet excitation and response to higher angles of attack. Flow visualization confirmed that the mechanism at peak buffeting had not changed, but had been merely shifted. It has been shown that the use of an optimum blowing profile could completely suppress the buffeting response without impairing the wing lift characteristics.