Low-frequency fluctuations and their suppression in the 5.5 m × 4 m aeroacoustic wind tunnel at CARDC

Abstract

Abstract This paper experimentally investigated characteristics of low-frequency pressure fluctuations in a large-scale open jet wind tunnel using pressure transducers and far-field microphones. Two distinct low-frequency pressure fluctuations have been detected at the range of wind speeds between 50\xa0m/s and 75\xa0m/s. The two peak frequencies vary with the change of wind speed. Analysis results show that both the low-frequency pressure fluctuations are driven by the resonances of the large scale instability waves in the jet shear layer at two different feedback loop paths. One loop is through the entire circuit of the wind tunnel, another exists between the nozzle and the collector, which is termed as edge-tone feedback. A formula for predicting the peak frequency was derived and the prediction agrees well with the measurement. In addition, an effective control strategy to suppress the wind tunnel circuit resonance and the edge-tone feedback resonance were also presented.