| Summary: | 碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 100 === The velocity measurement is an important item in various engineering field. Ultrasound is non-invasive, non- destroyed, high security, and attenuated lower than optical methods, so it is frequently applied to underwater measurement. This work establishes a pulsed ultrasonic Doppler system, which is based on scattering and Doppler-effect, consists of burst signal generator, power amplifier, transducer, pre- amplifier, oscilloscope, and digital signal processing software, Matlab. The measurement was conducted in a cavitation tank of uniform velocity distribution and the measured velocities were compared with a calibrated Pitot probe. By extracting the Doppler frequency shift, six flow velocities with three ultrasound projection angles were measured and the results of both velocities and flow directions matched very well with those of Pittot probe.
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