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 Flow Structure from Swept Edges Subjected to Controlled Motion

Unsteady Flow Structure from Swept Edges Subjected to Controlled Motion
Author:
Publisher:
Total Pages: 88
Release: 1990
Genre:
ISBN:

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This program addresses the unsteady flow structure and loading of delta wings subjected to controlled pitching motion. Efforts are focussed on three primary areas: generation of computer-aided techniques for quantitative interpretation of flow structure; development of new types of experimental instrumental and facilities; and characterization of the unsteady flow structure on delta wings. Computer applications for quantitative visualization of the vortex structure involve tracking of hydrogen bubble timelines and particles illuminated by scanning lasers. These techniques are integrated with active control systems that generate prescribed pitching motion of delta wings. Characterization of the unsteady flow structure is concerned with the response of the vortex breakdown to the motion of the wing and with preliminary consideration of the instantaneous cross-sectional structure of the leading edge vortices. The phase lag of these features of the flow structure, relative to the wing motion, is a central consideration.

Computation of a Kelvin-Helmholtz Instability for Delta Wing Vortex Flows

Computation of a Kelvin-Helmholtz Instability for Delta Wing Vortex Flows
Author: Raymond E. Gordnier
Publisher:
Total Pages: 44
Release: 1991
Genre: Airplanes
ISBN:

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The structure of the shear layer which emanates from the leading edge of a 76 degrees sweep delta wing and forms the primary vortex is investigated numerically. The flow conditions are M at infinity = 0.2, Re = 50,000 and angle of attack of 20.5 degrees. Computational results are obtained using a Beam- Warning type algorithm. The existence of a Kelvin-Helmholtz type instability of the shear layer which emanates from the leading edge of the delta wing is demonstrated. A description is provided of the three-dimensional, unsteady behavior of the small-scale vortices associated with this instability. The numerical results are compared qualitatively with experimental flow visualizations exhibiting similar behavior.

Controlled Vortical Flow on Delta Wings Through Unsteady Leading Edge Blowing

Controlled Vortical Flow on Delta Wings Through Unsteady Leading Edge Blowing
Author: National Aeronautics and Space Adm Nasa
Publisher:
Total Pages: 162
Release: 2018-11-18
Genre:
ISBN: 9781731351593

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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...