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Author : Daniel E. Fredberg
Publisher :
ISBN 13 :
Total Pages : 214 pages
Book Rating : 4.:/5 (318 download)
Download or read book PIV-based Examination of Dynamic Stall on an Oscillating Airfoil written by Daniel E. Fredberg and published by . This book was released on 2008 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Lawrence W. Carr
Publisher :
ISBN 13 :
Total Pages : 116 pages
Book Rating : 4.:/5 (31 download)
Download or read book Analysis of the Development of Dynamic Stall Based on Oscillating Airfoil Experiments written by Lawrence W. Carr and published by . This book was released on 1977 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Myung J. Rhee
Publisher :
ISBN 13 :
Total Pages : 112 pages
Book Rating : 4.:/5 (317 download)
Download or read book A Study of Dynamic Stall Vortex Development Using Two-Dimensional Data from the AFDD Oscillating Wing Experiment written by Myung J. Rhee and published by . This book was released on 2002 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study is to examine the previously unpublished instantaneous pressure data of the Aeroflightdynamics Directorate Two-Dimensional (2D) and Three-Dimensional (3D) Oscillating Wing Experiment to better understand the process of dynamic stall vortex development on the NACA 0015 airfoil. This report presents representative 2D instantaneous pressure data for the upper and lower surfaces of the airfoil at various chordwise locations obtained at specific angles of attack during upstroke and downstroke cycles. Furthermore, the report contains a complete set of plots of instantaneous pressure distributions for the upper surface for all the 2D data sets obtained in the experiment. First, the lift, drag and pitching moment data of various testing conditions are reviewed and analyzed to classify the data both with and without a boundary layer trip into "no stall," "moderate stall," and "deep stall" data. Next, instantaneous pressure distributions on the upper surface of the airfoil are examined for the study of vortex development. The lift and pitching moment data are analyzed to document the dynamic overshoot which delays the development of the stall on the airfoil. Next, the range of angles of attack are selected where the lift and pitching moment data shows significant changes from unsteady flow behavior daring oscillation cycles. Furthermore, based on the unsteady flow characteristics found in each classification of dynamic stall, analysis is continued to identify the conditions where the reduced frequency clearly affects the unsteady flow behavior of the airfoil during the oscillation. This can result in a change of the dynamic stall classification of the airfoil response under various unsteady flow conditions. These conditions are discussed in detail in the comparative studies.
Author : K. W. McAlister
Publisher :
ISBN 13 :
Total Pages : 80 pages
Book Rating : 4.:/5 (317 download)
Download or read book Suppression of Dynamic Stall with a Leading-edge Slat on a VR-7 Airfoil written by K. W. McAlister and published by . This book was released on 1993 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Bruce E. Brydges
Publisher :
ISBN 13 :
Total Pages : 116 pages
Book Rating : 4.:/5 (227 download)
Download or read book Flow Visualization of Dynamic Stall on an Oscillating Airfoil written by Bruce E. Brydges and published by . This book was released on 1989 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stroboscopic schlieren photography was used to investigate the effects of compressibility, reduced frequency, and amplitude on the dynamic stall of a NACA 0012 airfoil subjected to sinusoidal oscillation. The Mach number was varied from M at infinity = 0.25 to M at infinity = 0.45 (corresponding to a Reynolds number variation of Re = 450,000 to Re = 810,000); the reduced frequency was varied from k = 0.025 to k = 0.10. Oscillation amplitudes of alpha sub m = 5 deg and alpha sub m = 10 deg were compared. Schlieren photographs are presented, which document the dynamic stall vortex formation, convection, and shedding sequence for various experimental conditions. Additionally, a preliminary examination of the flow reattachment process was conducted. Data derived from the photographs indicates that increasing the compressibility causes dynamic stall to occur at lower angles of attack; while, increasing the reduced frequency and/or the oscillation amplitude effectively delays dynamic stall effects to a higher angle of attack. Flow reattachment is sensitive to both Mach number and reduced frequency for low values of these parameters; when either the Mach number or reduced frequency is sufficiently high, the reattachment process stabilizes. Keywords: Dynamic stall; Dynamic lift; Unsteady lift; Helicopter retreating blade stall; Oscillating airfoil; Flow visualization; Schlieren method. Theses. (jhd).
Author :
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (227 download)
Download or read book Flow Visualization of Dynamic Stall on an Oscillating Airfoil written by and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stroboscopic schlieren photography was used to investigate the effects of compressibility, reduced frequency, and amplitude on the dynamic stall of a NACA 0012 airfoil subjected to sinusoidal oscillation. The Mach number was varied from M at infinity = 0.25 to M at infinity = 0.45 (corresponding to a Reynolds number variation of Re = 450,000 to Re = 810,000); the reduced frequency was varied from k = 0.025 to k = 0.10. Oscillation amplitudes of alpha sub m = 5 deg and alpha sub m = 10 deg were compared. Schlieren photographs are presented, which document the dynamic stall vortex formation, convection, and shedding sequence for various experimental conditions. Additionally, a preliminary examination of the flow reattachment process was conducted. Data derived from the photographs indicates that increasing the compressibility causes dynamic stall to occur at lower angles of attack; while, increasing the reduced frequency and/or the oscillation amplitude effectively delays dynamic stall effects to a higher angle of attack. Flow reattachment is sensitive to both Mach number and reduced frequency for low values of these parameters; when either the Mach number or reduced frequency is sufficiently high, the reattachment process stabilizes. Keywords: Dynamic stall; Dynamic lift; Unsteady lift; Helicopter retreating blade stall; Oscillating airfoil; Flow visualization; Schlieren method. Theses. (jhd).
Author : R. D. VanDyken
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Leading Edge Velocity Field of an Oscillating Airfoil in Compressible Dynamic Stall written by R. D. VanDyken and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : M. S. Chandrasekhara
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Amplitude Effects on Dynamic Stall of an Oscillating Airfoil written by M. S. Chandrasekhara and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rush, Olive written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The folder may include clippings, announcements, small exhibition catalogs, and other ephemeral items.
Author : S. Ahmed
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Reattachment Studies of an Oscillating Airfoil Dynamic Stall Flow Field written by S. Ahmed and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : John Joseph Zolan
Publisher :
ISBN 13 :
Total Pages : 120 pages
Book Rating : 4.:/5 (436 download)
Download or read book Dynamic Stall on Airfoils in Oscillating Flow written by John Joseph Zolan and published by . This book was released on 1976 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Franklin O. Carta
Publisher :
ISBN 13 :
Total Pages : 108 pages
Book Rating : 4.:/5 (317 download)
Download or read book Analysis of Oscillatory Pressure Data Including Dynamic Stall Effects written by Franklin O. Carta and published by . This book was released on 1974 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamic stall phenomenon was examined in detail by analyzing an existing set of unsteady pressure data obtained on an airfoil oscillating in pitch. Most of the data were for sinusoidal oscillations which penetrated the stall region in varying degrees, and here the effort was concentrated on the chordwise propagation of pressure waves associated with the dynamic stall. It was found that this phenomenon could be quantified in terms of a pressure wave velocity which is consistently much less than free-stream velocity, and which varies directly with frequency. It was also found that even when the stall region has been deeply penetrated and a substantial dynamic stall occurs during the downstroke, stall recovery near minimum incidence will occur, followed by a potential flow behavior up to stall inception.
Author : Michel Pascazio
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Experimental and Numerical Investigation of Airfoil Dynamic Stall in Combined Pitch-translation Oscillation written by Michel Pascazio and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 4 pages
Book Rating : 4.:/5 (227 download)
Download or read book Velocity and Vorticity Distributions Over an Oscillating Airfoil Under Compressible Dynamic Stall written by and published by . This book was released on 1993 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The velocity and vorticity fields around an oscillating airfoil in compressible dynamic stall are reported. Phase averaged, two component laser velocimetry data were obtained at a freestream Mach number of 0.3 and a reduced frequency of 0.05. This is the first set of velocity data available at a high Reynolds number (540,000) under compressible flow conditions and it serves as a good database for development and validation of computer codes. Of particular interest is the formation of a separation bubble, which bursts coincidently with the formation of the dynamic stall vortex, adding an extra degree of physical complexity to the problem.
Author :
Publisher :
ISBN 13 :
Total Pages : 22 pages
Book Rating : 4.:/5 (318 download)
Download or read book Evaluation of Airfoil Dynamic Stall Characteristics for Maneuverability written by and published by . This book was released on 2000 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 many parameters that influence rotors in flight. For single-element airfoils it appears that 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. The loading on a helicopter blade during a severe maneuver is examined and it is shown that the blade's dynamic stall function is similar to that obtained in two-dimensional wind tunnel testing. An evaluation of three-dimensional effects for flight and an oscillating wing in a wind tunnel suggests that the two problems are not proper analogues. The utility of the dynamic stall function is demonstrated by evaluating sample theoretical predictions based on semi-empirical stall models and CFD computations. The approach is also shown to be useful in evaluating multi-element airfoil data obtained from dynamic stall tests.
Author : M. Chandrasekhara
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Flow Visualization Studies of the Mach Number Effects on the Dynamic Stall of an Oscillating Airfoil written by M. Chandrasekhara and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jaan Liiva
Publisher :
ISBN 13 :
Total Pages : 147 pages
Book Rating : 4.:/5 (227 download)
Download or read book Two-dimensional Tests of Airfoils Oscillating Near Stall. Volume I. Summary and Evaluation of Results written by Jaan Liiva and published by . This book was released on 1968 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation into rotor blade dynamic stall was conducted. Two typical airfoils, the NACA 0012 (modified) and the Vertol 23010-1.58, were tested by measuring the differential pressures acting during pitching and translatory oscillations over a range of angles of attack covering the stall regime. There were two main objectives. The first was to determine the influence of stall on the aerodynamic pitching moment of an airfoil executing pitching motions corresponding to the elastic torsional oscillations of a rotor blade. The second was to determine the extent to which time-varying angle of attack could affect the maximum aerodynamic lift that a rotor blade can develop. The cambered profile remained free of negative damping for 3 to 6 degrees beyond the point where the symmetrical section encountered negative damping in the Mach 0.2 to 0.4 range. The cambered section exhibited higher attainable C sub N's than the symmetrical section under all conditions of motion, except for the highest frequency tested at Mach 0.6. (Author).
