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Characterizing the noise patterns of overlapping propellers in forward flighta)
Burak Buda Turhan1, Hasan Kamliya Jawahar1, Djamel Rezgui1
1Department of Aerospace Engineering, University of Bristol, Bristol BS8 1TR, United Kingdom.
The Journal of the Acoustical Society of America
|April 14, 2025
Summary
Overlapping propellers in electric aircraft increase noise, especially tonal noise. Lateral separation is key to managing this, with significant noise increases observed at 40% propeller diameter spacing.
Area of Science:
- Acoustics
- Aerospace Engineering
- Sustainable Aviation
Background:
- Distributed electric propulsion (DEP) is crucial for sustainable aviation.
- Unconventional rotor placements in DEP systems can lead to increased noise pollution.
- Understanding propeller interactions is vital for noise reduction.
Purpose of the Study:
- To experimentally investigate the acoustic performance of overlapping propellers.
- To determine the effects of lateral and axial separation on noise levels.
- To identify the primary noise contributors and influencing factors.
Main Methods:
- Aeroacoustic wind tunnel experiments were conducted.
- A twin side-by-side propeller configuration with five-bladed propellers was used.
- Noise levels were analyzed under varying inflow conditions and rotational speeds.
Main Results:
- Tonal noise is the main contributor to increased sound pressure levels.
- Noise levels are highly sensitive to lateral propeller separation.
- A lateral distance of approximately 40% of the propeller diameter significantly elevates tonal noise by 14-18 dB.
Conclusions:
- Lateral separation distance is the dominant factor in propeller acoustic behavior.
- Blade-vortex and blade-wake interactions are primary drivers of noise.
- Axial separation has a secondary effect on acoustic performance.
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