To obtain an uncertainty of flowrate measurement using ultrasonic Doppler velocity profile method (UVP), experiments are carried out using the national standard calibration facility of water flowrate in Japan. Flowrate measurement is based on a multi-path measurement using three transducers. To generate a disturbed flow, obstacle plates are installed upstream of the test section. The maximum difference from the reference flowrate is over 2% when the measurement is performed at 8D downstream of the obstacle plate. At 25D downstream of the obstacle plate, the deviation is within the fundamental uncertainty level. The uncertainty caused by the upstream condition is negligible small for 25D downstream of the final disturbance, however it is estimated to 2.9% for 8D.

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