The cycloidal rotor is a novel configuration which has shown significant aerodynamic performance benefits when compared to a conventional rotor at MAV (Micro Air Vehicle) scale. The objective of the present study is to investigate the aeroacoustics of larger size UAV (Unmanned Aerial Vehicle) scale cycloidal rotors through a well-balanced experimental and computational approach. To predict the noise of the cycloidal rotor, an aeroacoustic framework is developed which consists of an aeroelastic model of the cycloidal rotor coupled to an acoustic solver. The aeroelastic framework of cycloidal rotor is developed by coupling a high fidelity unsteady aerodynamic model with a fully nonlinear geometrically exact beam model. The aerodynamic loads predicted by the aeroelastic model of cycloidal rotor are utilized by the acoustic solver to generate loading noise. The harmonic noise is predicted using Ffowcs Williams - Hawkings solver tailored to the kinematics of the cycloidal rotor. The aerodynamic and acoustic performance of cycloidal rotor predicted by the developed model is validated with results obtained from in-house experiments. For this purpose, systematic experiments were conducted to measure thrust, power and sound pressure level of a UAV scale cycloidal rotor while varying different rotor design parameters. The aeroacoustic framework is then utilized to understand the acoustic benefits of the cycloidal rotor. The aerodynamically generated noise of the cycloidal rotor is concentrated in the blade passing frequency, with little noise generated at higher harmonics. Due to the low operating rpm of the cycloidal rotor, this will lead to considerable decrease in A-weighted noise levels. The model developed in this paper can be utilized for design and optimization of quiet and efficient next generation cycloidal rotors.
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