Broadband noise simulation of small coaxial rotor configurations

Abstract

In small multirotor configurations such as eVTOL or drones, the broadband noise can become a dominant noise source. The low tip Mach number and disturbed rotor inflow can have a significant influence on both the noise spectra and the noise directivity, especially in high frequency. The broad-band noise of small multirotor configurations was simulated using DLR’s broadband noise code (BbaN) and compared with test results from DLR’s Acoustic Wind tunnel in Braunschweig (AWB). The boundary layer characteristics required for broadband noise predictions are derived with DLR’s free wake unsteady panel code UPM using viscous-inviscid coupling. The noise source characteristics and the contribution of the broadband noise are analyzed for different coaxial configurations and flight conditions.