Forced unsteady separated flows on a 45 degree delta wing

A great deal of current research activities has focused on possible exploitation of forced unsteady separated flows to provide enhanced lift and maneuvering characteristics. The formal and intentional utilization of these flows is currently being manifested in the form of the Advanced Tactical Fighter. The wing planform geometry of the ATF and other fighter aircraft is a delta wing. Under steady conditions, leading edge vortices are formed on each side of a delta wing. These vortices are mostly responsible for the attainment of lift to high angles of attack. Unsteady motion histories will likely alter the characteristics of this vortex as well as its development history. This will then present new difficulties in terms of lift enhancement and control. In order to successfully predict and optimally exploit the flight regimes offered by the ATF, greater understanding of the underlying physical mechanisms responsible for these unsteady flow fields must be obtained.;The vortex dominated flow fields produced by an oscillating 45 degree delta wing were examined across a wide range of unsteady motion histories. Still and high speed video photography were employed to document the flow development processes and cortex kinematics. Force balance data recorded the unsteady aerodynamic loading produced. These methods allowed for a thorough qualitative and quantitative examination of the flow fields elicited by a pitching delta wing. The wide range of motion histories employed were found to have a tremendous impact in terms of flow development lift enhancement, drag reduction and overall aerodynamic performance. Integrations of the data permitted speculation regarding the underlying physical mechanisms responsible for the observed phenomena. Experimental evidence allowed for hypotheses regarding the physical mechanisms of vorticity production, accumulation, convection and diffusion.