A method for mapping the separation and transition of flow over a slowly pitching airfoil with high angular resolution is presented. An array of surface-mounted hot-film sensors is used to record simultaneous corresponding voltages. The method makes use of windowed correlation and spectral signatures of hot-film sensor voltages in synchronization with a servo-motor controlling airfoil pitch angle. Results are given for a NACA-0012 airfoil at three airspeeds at pitch angles of less than 6 deg. The airspeeds correspond to a region of known aeroelastic instability; they are situated between chord Reynolds numbers of 50,000 and 130,000. Tests in static and quasi-static pitch motion schedules were conducted. The quasi-static airfoil was sinusoidally pitching at 0.025 Hz between −6 deg and +6 deg (corresponding to a half-chord based reduced frequency between 0.0011 and 0.0020) and the detected separation and transition agreed very well with the static case. These results constitute a verification of the method used and provide insight into the size and location of the laminar separation bubble at transitional Reynolds numbers.
Detection of Laminar Flow Separation and Transition on a NACA-0012 Airfoil Using Surface Hot-Films
Contributed by the Fluids Engineering Division of ASME for publication in the Journal of Fluids Engineering. Manuscript received October 2, 2012; final manuscript received April 9, 2013; published online August 6, 2013. Assoc. Editor: Zvi Rusak.
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Rudmin, D., Benaissa, A., and Poirel, D. (August 6, 2013). "Detection of Laminar Flow Separation and Transition on a NACA-0012 Airfoil Using Surface Hot-Films." ASME. J. Fluids Eng. October 2013; 135(10): 101104. https://doi.org/10.1115/1.4024807
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