Evaluation of measurement accuracy of a dealiasing method for use with ultrasonic pulsed Doppler

Ultrasonic pulsed Doppler method has a limitation that both the maximum measurable velocity and the length cannot be increased at the same time. In order to overcome this limitation, the dual PRF (pulse repetition frequency) method and the feedback method have been proposed for measuring flow rate in a pipe. In this study, a rotating cylinder device was employed for evaluating accuracy of the velocities obtained by means of the dealiasing methods. Effects of the velocity extension number, the measurement volume and the number of pulse repetition for obtaining an instantaneous velocity profile on the uncertainties of the velocities are evaluated be comparing standard deviations of the velocities. It is shown that the extension number has an optimum value in each condition, and it should be set as small as possible to avoid the velocity aliasing. Furthermore, increasing size of the measurement volume is more effective for improving the measurement uncertainty in comparison to increasing the number of pulse repetition.