0402 Effect of velocity extension on the velocity accuracy using ultrasonic pulsed Doppler method

Ultrasonic pulsed Doppler method (UDM) can obtain velocity profile along the ultrasonic beam path. However, the UDM has the limitation of the detectable velocity based on the measurement volume size. This problem was apparent when higher velocity were measured by using a velocity extension method. In order to investigate the accuracy of the velocity extension method, velocity distributions in a rotating cylinder were measured with changing of the measurement volume, and the relation between the maximum velocity required for the reflector to remain in the same measurement volume during the pulse interval, ν_, and the measured velocity was investigated. It was found that if measured velocities were higher than the ν_, the velocity accuracy dramatically decreased. Further, the tendency was more apparent with going away from the transducer.