Experimental Study of Aerodynamic and Aeroacoustic Effects of Installed Multi-Rotor in Non-Axial Flight

An experimental study is conducted on a tandem-rotor assembly in forward tilted flight to characterize the loading on each rotor and the far-field noise of the system. The assembly is collectively tilted to generate a range of transitional regimes where the rotors operate in highly non-axial inflow. The aerodynamic loading for a baseline configuration in this condition is presented as coefficients of thrust recorded at each rotor. Within this regime, the rear rotor demonstrates a different loading condition due to the change in flow-field induced by front rotor wake. The far-field noise is highly directive due to the mutual interaction between the rotors in the baseline configuration and is dominated by the first few blade passing harmonics. Altering the physical separations between the rotors changes the noise directivity and in some operating conditions led to a reduction of overall sound pressure levels at certain observer locations.