Wall pressure fluctuations generated by Turbulent Boundary Layers(TBL) provide a significant contribution in reducing the structural vibration and the aircraft cabin noise. However,it is difficult to evaluate these fl...Wall pressure fluctuations generated by Turbulent Boundary Layers(TBL) provide a significant contribution in reducing the structural vibration and the aircraft cabin noise. However,it is difficult to evaluate these fluctuations accurately through a wind tunnel test because of the pollution caused by the background noise generated by the jet or the valve of the wind tunnel. In this study, a new technology named Subsection Approaching Method(SAM) is proposed to separate the wall pressure fluctuations from the background noise induced by the jet or the valve for a transonic wind tunnel test. The SAM demonstrates good performance on separating the background noise from the total pressure compared to the other method in this study. The investigation considers the effects of the sound intensity and the decay factor on the sound-source separation. The results show that the SAM can derive wall pressure fluctuations effectively even when the level of background noise is considerably higher than the level of the wall pressure fluctuations caused by the TBL. In addition, the computational precision is also analyzed based on the broad band noise tested in the wind tunnel. Two methods to improve the precision of the computation with the SAM are also suggested: decreasing the loop gain and increasing the sensors for the signal analysis.展开更多
Large eddy simulation (LES) was used to investigate the space-time field of the low Mach number, fully developed turbulent boundary layer on a smooth, rigid flat plate. The wall-pressure field simulated by LES was ana...Large eddy simulation (LES) was used to investigate the space-time field of the low Mach number, fully developed turbulent boundary layer on a smooth, rigid flat plate. The wall-pressure field simulated by LES was analyzed to obtain the pressure statistics, including the wall-pressure root-mean square, skewness and flatness factors, which show the wall pressure distribution was not Gaussian. The profile of the auto-power spectral density and the contour of the streamwise wavenumber-frequency spectral density of wall-pressure were plotted. The "convection ridge" can be observed clearly and the convection velocity can be calculated from the location of the convection peak.展开更多
In this paper theoretical wall pressure fluctuation spectrum calculated by Rapid Distortion Theory was used to predict the effect of circular transducer size on the measured statistical properties of wall pressure flu...In this paper theoretical wall pressure fluctuation spectrum calculated by Rapid Distortion Theory was used to predict the effect of circular transducer size on the measured statistical properties of wall pressure fluctuation signals. It was found that the measured onedimensional spectrum has a significant decreaSe at hish wave numbers due to attenuation by the finite size of the transducer, and wall pressure fluctuahon intensity decreases with the increase of the transducer size.展开更多
Wall pressure fluctuation is one of the source terms which result in thevibration of hydraulic structures. To consider both the space and time correlation of the pressurefield. the method of proper orthogonal decompos...Wall pressure fluctuation is one of the source terms which result in thevibration of hydraulic structures. To consider both the space and time correlation of the pressurefield. the method of proper orthogonal decomposition and low-dimensional approximation were usedhere to describe the pressure signals of the turbulent boundary layer, the apron of the stillingpond and the vertically impinging jet.展开更多
文摘Wall pressure fluctuations generated by Turbulent Boundary Layers(TBL) provide a significant contribution in reducing the structural vibration and the aircraft cabin noise. However,it is difficult to evaluate these fluctuations accurately through a wind tunnel test because of the pollution caused by the background noise generated by the jet or the valve of the wind tunnel. In this study, a new technology named Subsection Approaching Method(SAM) is proposed to separate the wall pressure fluctuations from the background noise induced by the jet or the valve for a transonic wind tunnel test. The SAM demonstrates good performance on separating the background noise from the total pressure compared to the other method in this study. The investigation considers the effects of the sound intensity and the decay factor on the sound-source separation. The results show that the SAM can derive wall pressure fluctuations effectively even when the level of background noise is considerably higher than the level of the wall pressure fluctuations caused by the TBL. In addition, the computational precision is also analyzed based on the broad band noise tested in the wind tunnel. Two methods to improve the precision of the computation with the SAM are also suggested: decreasing the loop gain and increasing the sensors for the signal analysis.
基金The National Natural Science Foundation of China (No10772119)
文摘Large eddy simulation (LES) was used to investigate the space-time field of the low Mach number, fully developed turbulent boundary layer on a smooth, rigid flat plate. The wall-pressure field simulated by LES was analyzed to obtain the pressure statistics, including the wall-pressure root-mean square, skewness and flatness factors, which show the wall pressure distribution was not Gaussian. The profile of the auto-power spectral density and the contour of the streamwise wavenumber-frequency spectral density of wall-pressure were plotted. The "convection ridge" can be observed clearly and the convection velocity can be calculated from the location of the convection peak.
文摘In this paper theoretical wall pressure fluctuation spectrum calculated by Rapid Distortion Theory was used to predict the effect of circular transducer size on the measured statistical properties of wall pressure fluctuation signals. It was found that the measured onedimensional spectrum has a significant decreaSe at hish wave numbers due to attenuation by the finite size of the transducer, and wall pressure fluctuahon intensity decreases with the increase of the transducer size.
文摘Wall pressure fluctuation is one of the source terms which result in thevibration of hydraulic structures. To consider both the space and time correlation of the pressurefield. the method of proper orthogonal decomposition and low-dimensional approximation were usedhere to describe the pressure signals of the turbulent boundary layer, the apron of the stillingpond and the vertically impinging jet.
