Improvement of temporal resolution in ultrasonic pulsed Doppler method for multiphase flow

在不同脉冲重复次数(N_PULSE)和信噪比(SNR)的情况下，通过仿真和实验，比较了快速傅立叶变换(FFT)、自相关变换和小波变换(WT)等超声脉冲多普勒法的分析算法。我们证明了每个算法都有一个与信噪比有关的合适的N脉冲；具体地说，N脉冲的值随信噪比的降低而增加。WT相对不受噪声的影响。因此，小波变换是测量速度分布以提高时间分辨率的有效方法。

Analysis algorithms in ultrasonic pulsed Doppler method including the fast Fourier transform (FFT), autocorrelation, and the wavelet transform (WT) were compared via simulations and experiments using varying values of number of pulse repetition (N_pulse) and the signal-to-noise ratio (SNR). We show that there is an appropriate N_pulse for each algorithm that depends on the SNR; specifically, the value of N_pulse increases with decreasing SNR. The WT was relatively unaffected by noise. Therefore, a WT is the effective method for measuring velocity distributions for improving the temporal resolution.