Development of ultrasonic velocity-profiler system combining pulse-doppler and cross correlation techniques

Measurement techniques for turbulence flow by high time resolution have been developed using Ultrasonic Velocity Profiling technique. The signal processing algorithm affects the time resolution whose maximum of a conventional Ultrasonic Velocity Profiler (UVP) based on the pulse-Doppler signal is on the order of 10 ms, which is insufficient for the investigation of turbulence characteristics. We used a cross correlation technique to estimate a time difference between paired echo signals of ultrasound pulses emissions to improve the time resolution of the UVP. This technique is susceptible to noise, so that the frequently signals of velocity information may hardly be detected out of measured signals especially in such as metal pipes. To solve this issue, a novel signal processing technique by combining the pulsed-Doppler and the cross-correlation techniques has been developed, in which the maximum time resolution attained to be less than 500 μs and robustness against noise. The deviation of the measured mean velocity between this novel UVP and existing LDV is within 0.1% even in stainless pipe.