Title: An experimental study of flapping flight through imposed motion on a symmetric airfoil
Abstract:Four separate airfoil motions were investigated using surface pressure measurements, incorporating four imposed geometric or kinematic modifications. (1) A stationary NACA 0015 airfoil equipped with a...Four separate airfoil motions were investigated using surface pressure measurements, incorporating four imposed geometric or kinematic modifications. (1) A stationary NACA 0015 airfoil equipped with a full-span 25% chord plain trailing-edge flap (TEF), incorporating Gurney flaps (GF) of different flap heights and perforations, was investigated. (2) The impact of a dynamically deflected TEF, in conjunction with a Gurney flap, on a NACA 0015 airfoil subjected to a constant ramping or pitch-up motion was also examined. (3) The effects of a harmonically deflected trailing-edge flap, actuated at different start times and deflection amplitudes, on an oscillating NACA 0015 airfoil were investigated. (4) Finally, a NACA 0012 heaving airfoil with a super-imposed oscillation motion was studied. The surface pressure measurements were supplemented with particle-image velocimetry, hot-wire measurements, and smoke-flow visualizations. For the stationary airfoil, the combined GF and TEF led to a significant increase in the lift, drag, and pitching moment coefficient compared to that produced by independently deployed TEF or GF. The maximum effectiveness occurred with the smallest flap height. For the ramping airfoil, an earlier TEF actuation and shorter duration resulted in a larger maximum lift. The addition of a Gurney flap to the dynamic TEF led to a further increase in the maximum lift. For the oscillating airfoil, the observed change in the critical aerodynamic values were mainly produced by the drastic change in the pressure developed on both lower and upper surfaces of the flap. The formation and detachment of the leading-edge vortex were found to remain largely unaffected by the flap deflection, regardless of the flap actuation start time. The later the flap actuation the larger the change in the intensity of the leading-edge vortex. For the heaving airfoil, the aerodynamics were virtually unchanged over an entire combined motion cycle for the out-of-phase oscillation motion. The in-phase case persistently produced the best lift performance while suffering from a large nose-down pitching moment. The phase shift between the two motions was the key parameter to control the aerodynamic load generation.%%%%Quatre mouvements de profil aeronautique ont ete etudiees en utilisant des mesures de pression de surface, avec quatre modifications imposees de geometrie ou de cinematique. (1) Un profil NACA 0015 stationaire equipe d'un volet de bord de fuite (VBF) de 25% corde, incorporant des volets Gurney (VG) de differents hauteurs et perforations, a ete etudie. (2) L'impact d'un VBF devie dynamiquement, en conjonction avec un volet Gurney, sur un profil NACA 0015 soumis a un mouvement ramper a egalement ete etudie. (3) Les effets d'un volet de bord de fuite devie harmoniquement, actionne a differents moments et avec differentes amplitudes de deviation, sur un profil NACA 0015 oscillant ont ete etudies. (4) Finalement, un profil NACA 0012 avec une mouvement de translation, superposee par un mouvement oscillant, a ete etudiee. Les…Read More
Publication Year: 2017
Publication Date: 2017-01-01
Language: en
Type: article
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