The Unsteady Aerodynamics of a Delta Wing Undergoing Large Amplitude Pitching Motions

The goal of this study was to examine the relationship between the aerodynamic loads and the vortex flow characteristics of a highly swept delta wing 70 deg sweep undergoing both steady and unsteady pitching motions. The effects of several parameters were examined, including motion amplitude, pitching frequency, Reynolds number, and leading edge geometry. The unsteady surface pressure data could be separated into two regimes dependent on the angle of attack range a regime where quasi-steady behavior occurred, and a regime where significant unsteady effects occurred. The first regime included angle of attack ranges which precluded the occurrence of vortex breakdown, and ranges for which breakdown existed on the wing throughout the motions. The second regime included angle of attack ranges where breakdown moved onto or off of the wing, and ranges which included very high angles of attack involving full scale leeward flow separation. For the second regime, the unsteady effects occurred in the form of a hysteresis in the surface pressures relative to the steady case. It appeared that either the onset of breakdown or the reformation of the vortex system at very high incidences was responsible for the unsteady effects. Unsteady Aerodynamics, Dynamic Stall, Slender Wings, Flow Visualization.