Suppression of Dynamic Stall with a Leading-edge Slat on a VR-7 Airfoil PDF Download
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Author: K. W. McAlister
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 80
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Author: K. W. McAlister
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 80
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722792268
Category :
Languages : en
Pages : 76
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Book Description
The VR-7 airfoil was experimentally studied with and without a leading-edge slat at fixed angles of attack from 0 deg to 30 deg at Re = 200,000 and for unsteady pitching motions described by alpha equals alpha(sub m) + 10 deg(sin(wt)). The models were two dimensional, and the test was performed in a water tunnel at Ames Research Center. The unsteady conditions ranged over Re equals 100,000 to 250,000, k equals 0.001 to 0.2, and alpha(sub m) = 10 deg to 20 deg. Unsteady lift, drag, and pitching-moment measurements were obtained along with fluorescent-dye flow visualizations. The addition of the slat was found to delay the static-drag and static-moment stall by about 5 degrees and to eliminate completely the development of a dynamic-stall vortex during unsteady motions that reached angles as high as 25 degrees. In all of the unsteady cases studied, the slat caused a significant reduction in the force and moment hysteresis amplitudes. The reduced frequency was found to have the greatest effect on the results, whereas the Reynolds number had little effect on the behavior of either the basic or the slatted airfoil. The slat caused a slight drag penalty at low angles of attack, but generally increased the lift/drag ratio when averaged over the full cycle of oscillation. Mcalister, K. W. and Tung, C. Ames Research Center...
Author: L. Venkatakrishnan
Publisher: Springer Nature
ISBN: 9811551839
Category : Technology & Engineering
Languages : en
Pages : 555
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Book Description
This book includes select papers presented during the 16th Asian Congress of Fluid Mechanics, held in JNCASR, Bangalore, and presents the latest developments in computational, experimental and theoretical research as well as industrial and technological advances. This book is of interest to researchers working in the field of fluid mechanics.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 836
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 62
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The loading of an airfoil during dynamic stall is examined in terms of the augmented lift and the associated penalties in pitching moment and drag. It is shown that once stall occurs and a leading-edge vortex is shed from the airfoil there is a unique relationship between the augmented lift, the negative pitching moment, and the increase in drag. This relationship, referred to here as the dynamic stall function, shows limited sensitivity to effects such as the airfoil section profile and Mach number, and appears to be independent of such parameters as Reynolds number, reduced frequency, and blade sweep. For single-element airfoils there is little that can be done to improve rotorcraft maneuverability except to provide good static clmax characteristics and the chord or blade number that is required to provide the necessary rotor thrust. However, multi-element airfoils or airfoils with variable geometry features can provide augmented lift in some cases that exceeds that available from a single-element airfoil. The dynamic stall function is shown to be a useful tool for the evaluation of both measured and calculated dynamic stall characteristics of singleelement, multi-element, and variable geometry airfoils.
Author:
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 1484
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Author:
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 1168
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Author: D. Weaver
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 106
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Book Description
The Boeing-Vertol VR-7 airfoil was experimentally studied with steady and pulsed upper-surface blowing for sinusoidal pitching oscillations described by alpha = alpha(sub m) + 10 deg sin(omega t). The tests were conducted in the U.S. Army Aeroflightdynamics Directorate's Water Tunnel at NASA Ames Research Center. The experiment was performed at a Reynolds number of 100,000. Pitch oscillations with alpha(sub m) = 10 deg and 15 deg and with reduced frequencies ranging from k = 0.005 to 0.15 were examined. Blowing conditions ranged from C(sub mu) = 0.03 to 0.66 and F(+) = 0 to 3. Unsteady lift, drag, and pitching-moment loads were measured, and fluorescent-dye flow visualizations were obtained. Steady, upper-surface blowing was found to be capable of trapping a separation bubble near the leading edge during a portion of the airfoil's upward rotation. When this occurred, the lift was increased significantly and stall was averted. In all cases, steady blowing reduced the hysteresis amplitudes present in the loads and produced a large thrust force. The benefits of steady blowing diminished as the reduced frequency and mean angle of oscillation increased. Pulsed blowing showed only marginal benefits for the conditions tested. The greatest gains from pulsed blowing were achieved at F(+) = 0.9.
Author: American Helicopter Society
Publisher:
ISBN:
Category : Helicopters
Languages : en
Pages : 324
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Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 868
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