Investigation of Small-Scale Rotor Aeroacoustic in DLR's Acoustic Wind Tunnel Braunschweig

Abstract

This paper presents a multi-rotor test rig designed for the investigation of the aerodynamics and acoustics of small-scale propellers, relevant for urban air mobility vehicles applications. The test rig allows testing of isolated rotors, rotors in coaxial configurations and rotors in tandem configurations in various parametric combinations. Selected results are presented to emphasize the impact of aerodynamic and acoustic interaction effects on the characteristics of the acoustic emissions from multi-rotor configurations. The results indicate that amplification of harmonics and sub-harmonics noise components in the mid- to high-frequency range as well an increased broadband noise component are to be expected for such configurations. The work presented herein constitutes a first effort to experimentally investigate small-scale rotors to provide a database for the validation of numerical simulation schemes.