Delay of stall by small amplitude airfoil oscillation at low reynolds numbers

Research output: Contribution to conferencePaper

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Abstract

Particle Image Velocimetry and force measurements were conducted for small amplitude plunging motion of a NACA0012 airfoil at a post-stall angle of attack. Time-averaged flow shows that the region of separation is significantly reduced compared to a stationary airfoil. At low Strouhal numbers phase-averaged flow shows the formation and convection of leading-edge vortices, followed by their destructive interaction with the trailing-edge vortices. This mode of vortex flow is modified substantially at a critical Strouhal number. In this new mode, the leading-edge vortex is generated during the downward motion of the airfoil, but dissipates rapidly during the upward motion of the airfoil. Hence the convection of the leading-edge vortices is not observed. The strong interaction between the airfoil and vortex appears to destroy the coherency of the vortex. The switch between modes occurs at lower Strouhal numbers with increasing plunge amplitude. The critical Strouhal number corresponds to a Strouhal number based on the peak-to-peak amplitude SrA = 0.25 - 0.42. The point of drag to thrust switch correlates strongly with the point of mode-switch.

Conference

Conference47th AIAA Aerospace Sciences Meeting
CountryUSA United States
CityOrlando, Florida
Period5/01/098/01/09

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Reynolds number
vortex
oscillation
vortex flow
drag
thrust
convection

Cite this

Cleaver, D., Wang, Z., & Gursul, I. (2009). Delay of stall by small amplitude airfoil oscillation at low reynolds numbers. Paper presented at 47th AIAA Aerospace Sciences Meeting, Orlando, Florida, USA United States.DOI: 10.2514/6.2009-392

Delay of stall by small amplitude airfoil oscillation at low reynolds numbers. / Cleaver, David; Wang, Zhijin; Gursul, Ismet.

2009. Paper presented at 47th AIAA Aerospace Sciences Meeting, Orlando, Florida, USA United States.

Research output: Contribution to conferencePaper

Cleaver, D, Wang, Z & Gursul, I 2009, 'Delay of stall by small amplitude airfoil oscillation at low reynolds numbers' Paper presented at 47th AIAA Aerospace Sciences Meeting, Orlando, Florida, USA United States, 5/01/09 - 8/01/09, . DOI: 10.2514/6.2009-392
Cleaver D, Wang Z, Gursul I. Delay of stall by small amplitude airfoil oscillation at low reynolds numbers. 2009. Paper presented at 47th AIAA Aerospace Sciences Meeting, Orlando, Florida, USA United States. Available from, DOI: 10.2514/6.2009-392
Cleaver, David ; Wang, Zhijin ; Gursul, Ismet. / Delay of stall by small amplitude airfoil oscillation at low reynolds numbers. Paper presented at 47th AIAA Aerospace Sciences Meeting, Orlando, Florida, USA United States.
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abstract = "Particle Image Velocimetry and force measurements were conducted for small amplitude plunging motion of a NACA0012 airfoil at a post-stall angle of attack. Time-averaged flow shows that the region of separation is significantly reduced compared to a stationary airfoil. At low Strouhal numbers phase-averaged flow shows the formation and convection of leading-edge vortices, followed by their destructive interaction with the trailing-edge vortices. This mode of vortex flow is modified substantially at a critical Strouhal number. In this new mode, the leading-edge vortex is generated during the downward motion of the airfoil, but dissipates rapidly during the upward motion of the airfoil. Hence the convection of the leading-edge vortices is not observed. The strong interaction between the airfoil and vortex appears to destroy the coherency of the vortex. The switch between modes occurs at lower Strouhal numbers with increasing plunge amplitude. The critical Strouhal number corresponds to a Strouhal number based on the peak-to-peak amplitude SrA = 0.25 - 0.42. The point of drag to thrust switch correlates strongly with the point of mode-switch.",
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N2 - Particle Image Velocimetry and force measurements were conducted for small amplitude plunging motion of a NACA0012 airfoil at a post-stall angle of attack. Time-averaged flow shows that the region of separation is significantly reduced compared to a stationary airfoil. At low Strouhal numbers phase-averaged flow shows the formation and convection of leading-edge vortices, followed by their destructive interaction with the trailing-edge vortices. This mode of vortex flow is modified substantially at a critical Strouhal number. In this new mode, the leading-edge vortex is generated during the downward motion of the airfoil, but dissipates rapidly during the upward motion of the airfoil. Hence the convection of the leading-edge vortices is not observed. The strong interaction between the airfoil and vortex appears to destroy the coherency of the vortex. The switch between modes occurs at lower Strouhal numbers with increasing plunge amplitude. The critical Strouhal number corresponds to a Strouhal number based on the peak-to-peak amplitude SrA = 0.25 - 0.42. The point of drag to thrust switch correlates strongly with the point of mode-switch.

AB - Particle Image Velocimetry and force measurements were conducted for small amplitude plunging motion of a NACA0012 airfoil at a post-stall angle of attack. Time-averaged flow shows that the region of separation is significantly reduced compared to a stationary airfoil. At low Strouhal numbers phase-averaged flow shows the formation and convection of leading-edge vortices, followed by their destructive interaction with the trailing-edge vortices. This mode of vortex flow is modified substantially at a critical Strouhal number. In this new mode, the leading-edge vortex is generated during the downward motion of the airfoil, but dissipates rapidly during the upward motion of the airfoil. Hence the convection of the leading-edge vortices is not observed. The strong interaction between the airfoil and vortex appears to destroy the coherency of the vortex. The switch between modes occurs at lower Strouhal numbers with increasing plunge amplitude. The critical Strouhal number corresponds to a Strouhal number based on the peak-to-peak amplitude SrA = 0.25 - 0.42. The point of drag to thrust switch correlates strongly with the point of mode-switch.

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