Influence of obstacle plates on flowrate measurement uncertainty based on ultrasonic Doppler velocity profile method

To obtain the specific values of the flowrate measurement uncertainty using the ultrasonic Doppler velocity profile (UVP) method under disturbed flow conditions, experimental measurements were performed. To generate a disturbed flow, obstacle plates were installed upstream of the test section. To estimate which experimental parameter dominates the uncertainty, parametric examinations are conducted for the obstacle plate configuration, the distance between the obstacle plates and the measurement section, the incident angle of the ultrasonic beam, and the flowrate. The maximum deviation of the measured flowrate from the reference flowrate exceeds 2% when the flowrate is measured 8D downstream of the obstacle plate. At a distance of 25D downstream, the deviation is within the fundamental uncertainty level of the flowrate measurement using the UVP method. Because several uncertainty factors in this examination are cross-correlated with each other, the uncertainties of these factors are evaluated independently using analysis of variance (ANOVA). The total uncertainty is 7.98%, 1.97%, and 1.14% at 8D, 16D, and 25D, respectively.