Flow Visualization of Dynamic Stall on an Oscillating Airfoil PDF Download
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Author: Bruce E. Brydges
Publisher:
ISBN:
Category :
Languages : en
Pages : 116
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Book Description
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: Bruce E. Brydges
Publisher:
ISBN:
Category :
Languages : en
Pages : 116
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Book Description
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:
Category :
Languages : en
Pages : 0
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Book Description
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: M. Chandrasekhara
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Lawrence W. Carr
Publisher:
ISBN:
Category : Oscillating wings (Aerodynamics)
Languages : en
Pages : 116
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Book Description
Author: K.F. Tchon
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: C. M. Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 11
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Book Description
A solution procedure is presented for the computation of dynamic stall phenomena encountered by arbitrary shaped airfoils under arbitrary flow conditions. This procedure solves the unsteady, incompressible Navier-Stokes and the unsteady boundary layer equations using an efficient, zonal approach. A number of results for a modified NACA 0012 airfoil experiencing dynamic stall are presented and compared with available numerical data. Qualitative comparisons with flow visualization experiments are also presented. (Author).
Author: Kenneth W. McAlister
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 86
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Book Description
Author: S. Ahmed
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Todd Allen Brown
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 238
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Book Description
Author: Eric L. Pagenkopf
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 0
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Book Description
A Navier-Stokes problem solver, developed by L.N. Sankar, is modified to provide dynamic, interactive graphical presentations of predicted flow field solutions about a NACA-0012 airfoil section oscillating in pitch, in order to demonstrate the capabilities of dynamic graphics applications in the study of complex, unsteady flows. Flow field solutions in the form of pressure coefficient and stream function contour plots about an airfoil experiencing dynamic stall are plotted utilizing an IRIS 3000-series workstation and Graphical Animation System (GAS) software, developed by Sterling Software for NASA. These full cycle solutions in conjunction with dynamic surface pressure distribution plots and integrated lift, pitching moment and full cycle solutions, in conjunction with dynamic surface pressure distribution plots and integrated lift, pitching moment and drag coefficient data, are compared to existing experimental data in order to provide an indication of the validity of the code's far-field solution. Full procedural documentation is maintained in order to provide an efficient analysis tool for use in future oscillating airfoil studies planned by the NASA-Ames Fluid Mechanics Laboratory and the Naval Postgraduate School Department of Aeronautics and Astronautics. Keywords: Dynamic stall, Computer graphics, IRIS, Flow visualization, Theses. (jes).
