"This task addressed basic research to better understand unsteady, separated flows and to utilize this understanding to develop innovative concepts to control unsteady aerodynamic phenomena to enhance flight vehicle maneuverability. This effort sought to expand the flight performance boundaries by developing a capability to maneuver in the high-angle-of-attack, post-stall flight regime. ... The research was organized around two broad topical areas: (1) understanding and predicting the dynamics of unsteady, separated flows and (2) controlling unsteady, separated flows to enhance aerodynamic performance. Several types of flow fields were studied to gain an understanding of unsteady, separated flows. These included flow over rectangular wings, flow over delta wing, flow over forebodies and flow in the vicinity of the tail on a fighter type aircraft. The studies were both computational and experimental. Control efforts focused on the pulsed blowing to maintain attached flow, continuous blowing to control vortex breakdown on delta wing, and the use of neural networks to predict and control unsteady aerodynamic forces."--Summary.

This task addressed basic research to better understand unsteady, separated flows and to utilize this understanding to develop innovative concepts to control unsteady aerodynamic phenomena to enhance flight vehicle maneuverability. This effort sought to expand the flight performance boundaries by developing a capability to maneuver in the high-angle-of-attack, post-stall flight regime. The research was organized around two broad topical areas: (1) understanding and predicting the dynamics of unsteady, separated flows and (2) controlling unsteady, separated flows to enhance aerodynamic performance. Several types of flow fields were studied to gain an understanding of unsteady, separated flows. These included flow over rectangular wings, flow over delta wing, flow over forebodies and flow in the vicinity of the tail on a fighter type aircraft. The studies were both computational and experimental. Control efforts focused on the pulsed blowing to maintain attached flow, continuous blowing to control vortex breakdown on delta wing, and the use of neural networks to predict and control unsteady aerodynamic forces. (AN - analyst's abstract; delete this message when done).

The vortical flow over a delta wing contributes an important part of the lift - the so called nonlinear lift. Controlling this vortical flow with its favorable influence would enhance aircraft maneuverability at high angle of attack. Several previous studies have shown that control of the vortical flow field is possible through the use of blowing jets. The present experimental research studies vortical flow control by applying a new blowing scheme to the rounded leading edge of a delta wing; this blowing scheme is called Tangential Leading Edge Blowing (TLEB). Vortical flow response both to steady blowing and to unsteady blowing is investigated. It is found that TLEB can redevelop stable, strong vortices even in the post-stall angle of attack regime. Analysis of the steady data shows that the effect of leading edge blowing can be interpreted as an effective change in angle of attack. The examination of the fundamental time scales for vortical flow re-organization after the application of blowing for different initial states of the flow field is studied. Different time scales for flow re-organization are shown to depend upon the effective angle of attack. A faster response time can be achieved at angles of attack beyond stall by a suitable choice of the initial blowing momentum strength. Consequently, TLEB shows the potential of controlling the vortical flow over a wide range of angles of attack; i.e., in both for pre-stall and post-stall conditions. Lee, K. T. and Roberts, Leonard BLOWING; DELTA WINGS; FLOW DISTRIBUTION; LEADING EDGES; VORTICES; AIRCRAFT MANEUVERS; ANGLE OF ATTACK; MOMENTUM; NONLINEARITY; STABILITY...