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°. 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° and +6° (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
Transactions of the ASME, Series I. Journal of Fluids Engineering ; 135 , 10 ; 101105/1-101105/7
2013
7 Seiten, 15 Bilder, 22 Quellen
Aufsatz (Zeitschrift)
Englisch
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