强驻波声场中脉动速度特性

Study on vibrating velocity in high-intensity standing wave field

利用激光多普勒测速仪对管内空气强驻波声场中脉动速度特性进行了测量.实验结果表明:强声场对流场有很强的调制作用,使流场产生了与声波同频率的周期性脉动,且脉动幅度随着声场强度的增加而增大.管内声场强度不大时,实验值与理论值吻合较好;声场强度超过160dB后,出现了声湍流现象,实验测量值与理论计算值之间存在明显的偏差.当管内压力波幅处声场强度达到164dB时,距离反射板130mm位置处(sinkx=0.67)湍流脉动速度均方根值为3.50m/s,达到了该位置处脉动速度幅值的45%,表明强驻波场声湍流脉动非常剧烈.

The vibrating velocity in a high-intensity standing wave tube was measured by laser Doppler anemometry. The results show that the flow field is strongly modulated by intense acoustic field which makes the flow field vacillate with the sound wave synchronously. Moreover, the amplitude of vibrating velocity increases with increasing sound intensity. When sound intensity is not very high, the experimental results are consistent with the theoretical values. However, there is a distinct deviation between measured results and theoretical values when sound pressure level is higher than 160 dB, which indicates that the acoustically induced turbulence appears. When sound pressure level at the sound pressure loop reaches 164 dB, the rms turbulent velocity at the measuring position （ sinkx = 0. 67 ）, 130 mm from the reflecting plate, is 3.50 m/s, which is about 45% of the amplitude of vibrating velocity at the location. It is indicated that the acoustically induced turbulence in a high-intensity standing wave field is drastic.