Analysis of Acoustic Interference in Multi-Rotor Propulsion

Abstract

An intriguing concept of Regional and Urban Air Mobility is the distribution of propulsion across multiple propellers. However, a comprehensive exploration of the acoustic impact of these technologies is still lacking, despite its critical importance for operation in civil areas. Therefore, this study aims to deepen our understanding of the sound emission of such multipropeller configurations. An assessment of the interference effects between overlaying noise sources holds the potential to acoustically optimize these configurations.An analytical model to determine the noise radiation of open rotors in a low Reynolds number flow is presented and validated. The methodology combines the use of the Blade Element Momentum Theory to determine aerodynamics and an aeroacoustic model based on the acoustic analogy. This dual approach allows for the prediction of both self-noise and interaction noise sources. Furthermore, acoustic interference effects are displayed using a linear superposition model.Using this approach, various multipropeller configurations can be evaluated in terms of their sound radiation characteristics. A parameter study iterating key parameters like the spatial arrangement or phase shift of the propellers is conducted to identify configurations yielding low noise emissions.