The current study was conducted to understand flowfield unsteadiness associated with static stall hysteresis on a NACA 0012 airfoil at . Unsteady pressure measurements were acquired to evaluate the performance of the airfoil, and the presence of a hysteresis loop was identified in the vicinity of the airfoil . At poststall angles of attack, two fundamentally different flow regimes were observed between the upstroke and downstroke branches of the hysteresis loop. A Fourier analysis of the surface pressure distributions was used to attribute the flowfield unsteadiness to a low-frequency, high-amplitude oscillation in the flow near the leading edge, along with a regular bluff-body shedding frequency across the separated region of the airfoil. The low-frequency oscillations were observed to be more dominant for the upstroke branch, whereas the bluff-body shedding process was more dominant in the downstroke branch. Time-resolved particle image velocimetry data were acquired across the airfoil to qualitatively and quantitatively describe the low-frequency unsteadiness in the flow. These data were used to link the oscillations across the leading edge during the upstroke to a quasi-periodic surging of the flow, along with an advancement and retreating of the separation location across the surface.
Poststall Hysteresis and Flowfield Unsteadiness on a NACA 0012 Airfoil
AIAA Journal ; 56 , 7 ; 2528-2539
2018-03-28
12 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
Post-Stall Hysteresis and Flow Field Unsteadiness on an NACA 0012 Airfoil (AIAA 2017-0997)
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