开口风洞剪切层对传声器及其阵列测量影响试验研究
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摘要
开口风洞进行气动噪声测量及传声器阵列定位研究时必须考虑开口剪切层对声传播的影响。基于传统的二维剪切层折射修正公式的Snell定律和波传播对流效应,推导了更普遍的三维剪切层折射修正公式。针对0.55m×0.4m开口风洞,首先开展了风洞剪切层形态及位置的测量研究,70m/s风速下,该风洞剪切层略向外扩张,角度为1.14°;其次采用相位相关分析的方法研究了风速30,50和70m/s条件下,不同频段的声波穿过剪切层的折射现象,并与基于剪切层无限薄假设的Amiet等人的理论结果进行了比较,指出了折射角度的理论修正公式只有当声源到剪切层的距离大于4倍的目标声波波长时,即满足远场条件时,才与试验结果接近;最后,将剪切层修正方法应用于基于Beam-forming算法的传声器阵列的声源定位中,结果表明三维剪切层修正方法能够有效提高传声器阵列声源定位的准度。
The open jet shear layer has obvious effects on sound propagation.These effects must be carefully taken into account when using microphones to measure the aero-acoustic sources in jet,especially using microphone array to locate the sound sources.A three dimensional shear layer refraction correction method is derived which is based on the Snell's law and the wave convection effects in the jet.The shear layer refraction correction method is then applied in the specified 0.55 mby 0.4 mopen jet wind tunnel.Firstly,the shape and location of the shear layer of the wind tunnel is measured by the total pressure rake.The results show that the wind tunnel jet shear lay is slightly outspread at wind speed of 70 m/s,with the spread angle about 1.14°.Then,the shear layer refraction angle is measured by correlating the phases of two microphones outside the jet shear layer at wind speeds of 30,50 and 70 m/s.The measured results show that the Amiet's shear layer refraction theory does not always agree well with the test results.The application scope of the theory is that the distance between the shear layer and the aim source is less than four times the research target wavelength.Out of this scope,the Amiet's shear layer refraction theory may introduce significant error.At last,the three dimensional shear layer refraction correction method is used in the sound source localization measurement by microphone array with beam-forming algorithm.The results are then compared to the average Mach number method which is widely used in the beam-forming algorithm of microphone array.Both the three dimensional shear layer refraction correction method and the average Mach number methods can improve the source positioning accuracy.
The open jet shear layer has obvious effects on sound propagation.These effects must be carefully taken into account when using microphones to measure the aero-acoustic sources in jet,especially using microphone array to locate the sound sources.A three dimensional shear layer refraction correction method is derived which is based on the Snell's law and the wave convection effects in the jet.The shear layer refraction correction method is then applied in the specified 0.55 mby 0.4 mopen jet wind tunnel.Firstly,the shape and location of the shear layer of the wind tunnel is measured by the total pressure rake.The results show that the wind tunnel jet shear lay is slightly outspread at wind speed of 70 m/s,with the spread angle about 1.14°.Then,the shear layer refraction angle is measured by correlating the phases of two microphones outside the jet shear layer at wind speeds of 30,50 and 70 m/s.The measured results show that the Amiet's shear layer refraction theory does not always agree well with the test results.The application scope of the theory is that the distance between the shear layer and the aim source is less than four times the research target wavelength.Out of this scope,the Amiet's shear layer refraction theory may introduce significant error.At last,the three dimensional shear layer refraction correction method is used in the sound source localization measurement by microphone array with beam-forming algorithm.The results are then compared to the average Mach number method which is widely used in the beam-forming algorithm of microphone array.Both the three dimensional shear layer refraction correction method and the average Mach number methods can improve the source positioning accuracy.
引文
[1]Sanford J.Acoustic refractions:a three-dimensional shear layer correction for microphone measurements in an open-jet acoustic wind tunnel[J].Journal of Undergraduate Research,2008,10:1-12.
[2]Thomas J Mueller.Aeroacoustic measurements[M].Berlin:Springer,2002.
[3]Miles J W.On the reflection of sound at an interface of relative motion[J].JASA,1957,29(2):226-228.
[4]Ribner H S.Refraction,transmission,and amplification of sound by a moving medium[J].JASA,1957,29(4):435-441.
[5]Schlinker R H,Amiet R K.Experimental assessment of theory for refraction of sound by a shear layer[R].NASA Contractor Report145359,1978.
[6]Schlinker R H,Amiet R K.Shear layer refraction and scattering of sound[R].AIAA-80-0973,1980.
[7]Schlinker R H,Amiet R K.Refraction and scattering of sound by a shear layer[R].NASA Contractor Report 3371,1980.
[8]Candel S M,Guedel A,Julienne A.Radiation,refraction,and scattering of acoustic waves in a free shear layer flow[R].AIAA-76-544,1976.
[9]Ahuja K K,Tester B J,Tanna H K.An experimental study of transmission,reflection and scattering of sound in a free jet flight simulation facility and comparison with theory[J].J Sound and Vib,1985,75(1):51-85.
[10]van Ditshuizen J C A,Courage G D,Ross R,et al.Acoustic wave propagation through shear layer of the german-dutch open jet wind tunnel(DNW)[R].AIAA-83-0146,1983.
[11]Zana S.Effect of open-jet shear layers on aeroacoustic wind tunnel measurements[R].Delft:Delft University of Technology,2011.
[12]Sijtsma P.Phased array beamforming applied to wind tunnel and fly-over tests[R].NLR-TP-2010-549,2010.
[2]Thomas J Mueller.Aeroacoustic measurements[M].Berlin:Springer,2002.
[3]Miles J W.On the reflection of sound at an interface of relative motion[J].JASA,1957,29(2):226-228.
[4]Ribner H S.Refraction,transmission,and amplification of sound by a moving medium[J].JASA,1957,29(4):435-441.
[5]Schlinker R H,Amiet R K.Experimental assessment of theory for refraction of sound by a shear layer[R].NASA Contractor Report145359,1978.
[6]Schlinker R H,Amiet R K.Shear layer refraction and scattering of sound[R].AIAA-80-0973,1980.
[7]Schlinker R H,Amiet R K.Refraction and scattering of sound by a shear layer[R].NASA Contractor Report 3371,1980.
[8]Candel S M,Guedel A,Julienne A.Radiation,refraction,and scattering of acoustic waves in a free shear layer flow[R].AIAA-76-544,1976.
[9]Ahuja K K,Tester B J,Tanna H K.An experimental study of transmission,reflection and scattering of sound in a free jet flight simulation facility and comparison with theory[J].J Sound and Vib,1985,75(1):51-85.
[10]van Ditshuizen J C A,Courage G D,Ross R,et al.Acoustic wave propagation through shear layer of the german-dutch open jet wind tunnel(DNW)[R].AIAA-83-0146,1983.
[11]Zana S.Effect of open-jet shear layers on aeroacoustic wind tunnel measurements[R].Delft:Delft University of Technology,2011.
[12]Sijtsma P.Phased array beamforming applied to wind tunnel and fly-over tests[R].NLR-TP-2010-549,2010.
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