Buffeting flows over delta wings

Experimental evidence suggests that vortex breakdown is not the only source of buffeting of delta wings and fins. Other unsteady flow phenomena that c ontribute to buffeting at high angles of attack are fluctuations of vortex breakdown location and vortex shedding. Flow visualization and velocity mea surements were carried out over a delta wing, over a wide range of angles o f attack, to understand the transition between the helical mode instability and the vortex shedding. It was found that this transition is abrupt, as i ndicated by a jump in the frequency parameter, and that it occurs at the an gle of attach at which breakdown reached the apex, The unsteady nature of v ortex breakdown location was investigated by flow visualization for the int eraction of vortex: breakdown with a rigid Rat plate. Although there are in dications of a feedback effect an vortex breakdown, the amplitude of the fl uctuations of breakdown location is smaller for impinging flows.