Measuring the Acoustic Characteristics of a Helicopter Rotormodel in a Wind Tunnel

Abstract

The article presents the results of comparative experimental and computational studies of the acoustic characteristics of the model of a helicopter rotor performed in the modernized test section of the T-1K wind tunnel (WT). In order to identify and minimize the influence of spurious reflections on the studied acoustic characteristics using the Maximum Length Sequence method (M-sequence method) in the T-1K WT, we analyzed the microphone arrangement, which showed that the largest spurious contribution to the measured signal comes from reflections from the WT T-1K wall located behind the microphones. Comparison of the experimentally measured noise levels with the wall raised and lowered confirmed that the wall influences the measured acoustic noise characteristics of the model rotor. Comparison of experimental data with numerical simulation results allowed the conclusion that the WT T-1K modernized wind tunnel is fundamentally suitable to validate numerical methods of calculating the aeroacoustic characteristics of model rotors.