Zhang Jun, Wang Xunnian, Chen Zhengwu, Zhang Junlong «A study of the localization and quantification of noise sources using an inflow-speaker calibration» Тезисы докладов Шестой открытой Всероссийской (XVIII научно-технической) конференции по аэроакустике (22–27 сентября 2019 г.), с. 64 (2019)

Aeroacoustic tests are preferred to be performed in open-jet wind tunnels. Shear layer causes phase and amplitude distortion of sound during the propagation of sound from the inside to the outside of open-jet flow. The phase and amplitude of sound must be corrected for accurate localization and quantification of sound sources using a microphone array. In this study, a new method of correcting shear-layer effect is proposed. The transfer function of sound is obtained using an inflow-speaker calibration. The cross- spectrum matrix of the measured sound pressure is then corrected according to the transfer function, which is later used as an input for the noise map generation using beamforming. Experiment studies were performed in the 0.55m by 0.4m aeroacoustic wind tunnel in China Aerodynamics Research and Development Center. A comparison study was made between the present method and the traditional shear-layer correction method, e.g., Amiet’s method. More accurate estimation of the location and amplitude of noise source were obtained using the proposed method.

Zhang Jun, Wang Xunnian, Chen Zhengwu, Zhang Junlong «A study of the localization and quantification of noise sources using an inflow-speaker calibration» Тезисы докладов Шестой открытой Всероссийской (XVIII научно-технической) конференции по аэроакустике (22–27 сентября 2019 г.), с. 64 (2019)

Aeroacoustic tests are preferred to be performed in open-jet wind tunnels. Shear layer causes phase and amplitude distortion of sound during the propagation of sound from the inside to the outside of open-jet flow. The phase and amplitude of sound must be corrected for accurate localization and quantification of sound sources using a microphone array. In this study, a new method of correcting shear-layer effect is proposed. The transfer function of sound is obtained using an inflow-speaker calibration. The cross- spectrum matrix of the measured sound pressure is then corrected according to the transfer function, which is later used as an input for the noise map generation using beamforming. Experiment studies were performed in the 0.55m by 0.4m aeroacoustic wind tunnel in China Aerodynamics Research and Development Center. A comparison study was made between the present method and the traditional shear-layer correction method, e.g., Amiet’s method. More accurate estimation of the location and amplitude of noise source were obtained using the proposed method.

Wang Xiansheng, Wu Junqiang, Lu Bo, Yang Dangguo, Zhou Fangqi «Active control of acoustic resonance in a subsonic cavity flow» Тезисы докладов Шестой открытой Всероссийской (XVIII научно-технической) конференции по аэроакустике (22–27 сентября 2019 г.), с. 182 (2019)

The cavity-type flow often occurs in aeronautic engineering applications. When air flows over a cavity in high speed, flow-induced oscillations usually dominate the flow Held, accompanied by strong aerodynamic noise and acoustic resonance, which always bring about adverse effects on flight safety. An active control method based on the leading edge jet is proposed to suppress the flow-induced oscillations. The leading-edge jet is generated with a large blowing rate by guiding the incoming flow into a channel in front of the cavity. The control method is validated using high-speed wind tunnel experiments. The Mach number of the incoming flow is 0.6–0.9 and the cavity length-depth ratio is 6. The unsteady dynamic pressure measurement provides a way to study the characteristics of the cavity flow- induced oscillation and aeroacoustic loads. The results show that the strongest pressure fluctuation appears near the trailing-edge of the cavity, and the overall sound pressure level can be up to 176 dB. When the upstream injection is formed, the pressure fluctuations inside the cavity can be significantly suppressed not only in the broadband noise but also the cavity tones. The overall sound pressure level in the cavity can be reduced by up to 8 dB. Owing to no need of additional air supply to form high-speed upstream injection, the active control method can effectively suppress the subsonic cavity flow-induced oscillation, and the method provides a potential candidate strategy to control the cavity flow and acoustic resonance in the cavity-type engineering applications.

Chen Bao, Bao Anyu, Zhou Guocheng «Wind tunnel test technologies investigation of civil transport airframe/jet noise installation» Тезисы докладов Шестой открытой Всероссийской (XVIII научно-технической) конференции по аэроакустике (22–27 сентября 2019 г.), с. 77-79 (2019)

Airframe/jet installation noise is one of the main noise sources of civil aircraft. In order to reduce the noise of civil aircraft and acquire the overall noise characteristics of civil aircraft, it is necessary to acquire the sound pressure level, frequency spectrum characteristics of the airframe/jet installation noise and the effect rules of the relative position in the wind tunnel. In order to study the mechanism and characteristics of airframe/jet installation noise in aeroacoustic wind tunnel, the experimental method of airframe/jet installation noise in 0.5m aeroacoustic wind tunnel of AVIC ARI is studied in this paper. The nozzle noise simulation setup, wing support device and directivity measurement array are designed, and the experiment system is formed. The nozzle simulation setup can be installed with variable diameter nozzle, the position of the wing can be changed in the direction of axis and height. The diameter of the microphone phase array is lm, the number of microphones is 63, the distance from the nozzle center is 1.2m, the radius of the directivity arc is 1.8m, the directivity angle is 45–135 degrees and 225–315 degrees respectively with the interval 9 degress between microphones. Microphones are equipped with windproof balls. Secondly, the NACA0012 wing with 127mm chord length and the nozzle with the diameter D 25.4mm are tested in 0.5m aeroacoustic wind tunnel. The noise characteristics of airframe/jet installation effect were studied experimentally. The jet Mach number was 0.9, the free flow Mach number was 0.2, and the height and axial relative position ranges were 0.5D and 1.0D, respectively. The experiment data were obtained. Finally, based on the experiment data, the influence of the relative position of airframe and jet on the noise was analyzed and discussed. The results show that the existence of wing makes the azimuth angle 90 degree point noise. Acoustic pressure level increases to 5 dB, the change of relative position in the axis has little effect on directivity, and the noise pressure level increases when the wing is close to the nozzle in the height direction.