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Utilization of I-Q signals of ultrasound Doppler velocimeter to obtain 1-D turbulence quantities in pipe flow

机译：利用超声多普勒测速仪的I-Q信号获得管道流动中的一维湍流量

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摘要

A new method based on using inphase-quadrature (I-Q) ultrasound (US) signals was developed in order to overcome time resolution limitations encountered in turbulent flow measurements by ultrasound Doppler velocimetry (UDV). First, mathematical relations to be used in obtaining probability density function (PDF) and auto correlation function (ACF) of randomly fluctuating velocity (u) in the probe direction were derived in the form of the experimental I-Q signals. The results were evaluated with respect to those obtained by UDV or other conventional techniques whenever possible. In terms of general trend, velocity PDFs obtained from analytical relation along with the I-Q signals and from UDV compare well with each other for Reynolds numbers (N_(Re)) of 16730 and 26300 at the pipe center. Smaller standard deviation of velocity PDF from spectrum of I-Q US signals than that of UDV measurements was the only major difference that could be attributed to the enhanced time resolution of the former technique. Effect of increased time resolution was also observed in the measurement of velocity auto correlation coefficients (ACC). Time correlations of the velocity fluctuations could be captured by using I-Q signals as opposed to UDV that resulted in correlations going to zero in one or two time steps. ACC from I-Q signals was used to get turbulence spectrum at the pipe center. In addition Reynolds number and radial position dependency of integral and Taylor microlength scales, Kolmogorov length scale, rate of energy dissipation and eddy diffusion coefficient were also established.
机译：为了克服超声多普勒测速仪（UDV）在湍流测量中遇到的时间分辨率限制，开发了一种基于使用同相正交（I-Q）超声（US）信号的新方法。首先，以实验I-Q信号的形式推导了用于获得沿探针方向随机波动速度（u）的概率密度函数（PDF）和自相关函数（ACF）的数学关系。尽可能对通过UDV或其他常规技术获得的结果进行评估。就总体趋势而言，对于管道中心处的雷诺数（N_（Re））为16730和26300，从解析关系以及I-Q信号和UDV获得的速度PDF相互比较。 I-Q US信号频谱的速度PDF的标准偏差比UDV测量的小，这是可以归因于前一种技术的增强的时间分辨率的唯一主要区别。在速度自动相关系数（ACC）的测量中，还观察到时间分辨率提高的效果。速度波动的时间相关性可以通过使用I-Q信号来捕获，这与UDV相反，后者导致相关性在一到两个时间步中变为零。来自I-Q信号的ACC用于获得管道中心的湍流频谱。此外，还建立了积分和泰勒微尺度的雷诺数和径向位置依赖性，Kolmogorov尺度，能量耗散率和涡流扩散系数。

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