Vortex Breakdown Over Unsteady Wings and Its Control

Vortex Breakdown Over Unsteady Wings and Its Control
Author:
Publisher:
Total Pages: 87
Release: 1995
Genre:
ISBN:

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Control of vortex breakdown continues to be of vital importance because the breakdown may have a considerable effect on aircraft performance, such as the effect on the time-averaged lift force (Lee and Ho, 1990). Breakdown is also important because of the unsteady nature of flow downstream of vortex breakdown. The unsteadiness may affect the stability of the aircraft and also cause buffeting. The objectives of this work are to understand the physics of unsteady flow phenomena in vortex breakdown region, and to develop techniques for active (feedback) and passive (open loop) control of vortex breakdown over steady and unsteady delta wings.

Unsteady Structure of Leading-Edge Vortices on a Delta Wing

Unsteady Structure of Leading-Edge Vortices on a Delta Wing
Author:
Publisher:
Total Pages: 8
Release: 1994
Genre:
ISBN:

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The overall objective of this research program was to characterize the unsteady flow structure on wings having swept edges. Wings were subjected to global control, involving motion of the entire wing, and local control, involving perturbations at specified locations on the surface of the wing. New types of experimental facilities and image acquisition and processing techniques have allowed determination of the instantaneous vorticity distributions and streamline patterns of the flow. The occurrence of vortex breakdown and stall and their phase shifts relative to the wing motion and to control at the leading-edges have been interpreted in terms of new flow mechanisms. Delta Wings, Vortex Breakdown, Laser Diagnostics.

Unsteady Aerodynamics

Unsteady Aerodynamics
Author: Eric Joe Stephen
Publisher:
Total Pages:
Release: 1995
Genre: Lift (Aerodynamics)
ISBN:

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"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.

Unsteady Three-dimensional Aerodynamic Flow

Unsteady Three-dimensional Aerodynamic Flow
Author: Donald Rockwell
Publisher:
Total Pages: 10
Release: 1997
Genre: Airplanes
ISBN:

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The overall objective of this program is to determine the instantaneous flow structure on delta wings at high angle of attack as well as from cylindrical bodies, which are subjected to basic classes of motion. New techniques of high image density particle image velocimetry provide the instantaneous vorticity fields and streamline patterns, thereby allowing interpretation of the underlying physics using critical point theory. This type of quantitative interpretation of the flow structure is crucial for performing vorticity balances on wings and bodies and thereby optimization of overall performance characteristics. Furthermore, for the case of the delta wing at high angle of attack, local control techniques are applied simultaneously at leading and trailing edges of the wing, in order to alter the crucial features of vortex breakdown and subsequent large scale stall. Such control techniques have application to a wide variety of separated flows from wings and cylindrical bodies.