Attenuation of low-frequency pressure fluctuations within the test section of an aeroacoustic wind tunnel using Helmholtz resonators

Kurzfassung

A new aeroacoustic wind tunnel with an open test section was built at the University of Siegen. During the operation, infrasound tonal components and overtones reaching almost 110 dB in amplitude could be observed, sometimes influencing the measurements due to induced vibration of the wind tunnel structure. The present paper demonstrates the application of Helmholtz resonators on a pilot basis, which successfully attenuated these low-frequency peaks drastically. A systematic analysis using Helmholtz resonators with varying neck lengths was conducted. A single Helmholtz resonator, though able to tackle a target frequency, wasn't enough to get rid of other low-frequency components, leading to the use of two resonators. Additionally, the first application of the wind tunnel is shown to get an idea of its capabilities.