Aerodynamic and Aeroacoustic Study of Low Reynolds Number Rotors: Influence of Pitch Angle, Airfoil Camber and Thickness
Résumé
With the increase in the use of micro air vehicles (MAVs), the issue of noise pollution is becoming critical in both military and civilian fields. The main noise component in quadcopter MAVs is generated by the rotors and their interactions with the whole body. Here, a Non-Linear Vortex Lattice/Particle Method (NVLM), coupled with the Farassat formulation-1A of the Ffowcs-Williams and Hawkings (FW-H) acoustic analogy, is used to characterize the influence of the blade pitch and the airfoil shape on the tonal noise and the aerodynamic performance of low Reynolds number rotors typical of MAVs. The validation of both NVLM and FW-H codes is adressed with test cases from the literature and experiments on a 25cm diameter NACA0012 constant-pitch rotor in hovering conditions. The tonal noise of this MAV rotor is then studied in details. Finally, a parametric study of rotor pitch angle and of airfoil camber and thickness is performed, providing guidelines for the design of small rotors with low acoustic footprint and optimal aerodynamic performance.
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