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.

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.

Xingqiang Liu, Wenchao Huang, Hao Yan, Hongli Li «Tandem cylinder noise characteristics research and advance noise reduction method exploration» Тезисы докладов Шестой открытой Всероссийской (XVIII научно-технической) конференции по аэроакустике (22–27 сентября 2019 г.), с. 203-206 (2019)

With the reduction of jet noise associated with high pass ration engines on large civil transport aircraft. The airframe noise has become a primary noise source during takeoff and landing. A major component of airframe noise is the deployed landing gear. The configuration of landing is very complex; noise originates from the flow separation due to complex buff bodies and the wake flow multiple interactions with downstream components. Tandem cylinder represents generic flow geometry relevant to landing gear. The major interest is the nature of interaction of unsteady wake from upstream cylinder with the downstream cylinder. Wake interactions are expected to have a big impact on the noise generation. Experiment has been performed in this paper to access the noise characteristics, basing on the mechanism of noise generation, some advance control methods, such as plasma and turbulence, were used to reduce the noise.

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.