Author: K.F. Tchon
Publisher:
ISBN:
Category :
Languages : en
Pages :

Get Book Here

Book Description

Author: Bruce E. Brydges
Publisher:
ISBN:
Category :
Languages : en
Pages : 116

Get Book Here

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: Lawrence W. Carr
Publisher:
ISBN:
Category : Oscillating wings (Aerodynamics)
Languages : en
Pages : 116

Get Book Here

Book Description

Author: Todd Allen Brown
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 238

Get Book Here

Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Get Book Here

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: Charles Paul Gendrich
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 344

Get Book Here

Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 11

Get Book Here

Book Description
Compressibility effects on the flowfield of an airfoil executing rapid transient pitching motion from 0-60 deg over a wide range of Mach numbers and pitching rates were studied using a stroboscopic schlieren flow visualization technique. The studies have led to the first direct experimental documentation of multiple shocks on the airfoil upper surface flow for certain conditions. Also, at low Mach numbers, additional coherent vortical structures were found to be present along with the dynamic stall vortex, whereas at higher Mach numbers the flow was dominated by a single vortex. The delineating Mach number for significant compressibility effects was 0.3 and the dynamic stall process was accelerated by increasing the Mach number above that value. Increasing the pitch rate monotonically delayed stall to angles of attack as large as 27 deg.

Author: M. Chandrasekhara
Publisher:
ISBN:
Category :
Languages : en
Pages :

Get Book Here

Book Description

Author: G. M. Graham
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 102

Get Book Here

Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 69

Get Book Here

Book Description