EARLY VORTEX BURST ON A DELTA-WING IN PITCH

Wind-tunnel experiments were performed at a Mach number of 0.13 and Re ynolds number of 1.43 X 10(6) to study the flow over a 70-deg sharp le ading-edge delta wing model. The model was tested with the angle of at tack static, a sinusoidal oscillation, and a sinusoidal ramp up. Smoke flow visualization of the leading-edge vortices was used as well as s ix-component balance measurements for the delta wing forces and moment s. During the upstroke of a sinusoidal oscillation in pitch the vortex breakdown point was seen to reach the trailing edge at a significantl y lower angle of attack than in the static case. However, at large ang le of attack, its position lagged that of the static case. The dynamic normal force was less than the static value at angles of attack where the burst point led the static value and was higher when the burst po int lagged. A ramped pitch-up motion terminating at 24-deg angle of at tack produced lower lift and normal force values when compared to the static values. Furthermore, on cessation of the motion, the dynamic lo ads did not converge to their static values. This behavior was also at tributed to the lead in the burst point position during a pitch-up at low angles of attack.