CFD Study of Calibration Factor for Cross Correlation Based Ultrasonic Flowmeter at Different Upstream Pipe Lengths

Despite lots of researches on the transit-time and Doppler flowmeter technologies, few researches have been done on ultrasonic cross correlation flowmeter technology. Since the mechanism of the ultrasonic cross correlation flowmeter (UCCF) differs from other ultrasonic flowmeter technologies, it strongly requires individual investigations. The upstream straight pipe length is an important item that strongly affects the UCCF accuracy. Determination of proper calibration factor concerning upstream pipe length could incredibly improve the measurement precision. In the present study, the Computational Fluid Dynamics (CFD) simulation was conducted and the water flow inside a pipe without any flow disturbances (e.g., valve, fitting, or bend) was simulated to investigate the calibration factor for the UCCF at different upstream straight pipe lengths and different Reynolds numbers (from 76,600 to 383,400). For accurately predicting the turbulent flow behavior, Reynolds Stress Model (RSM) was used in this study. The results indicated that by increasing the upstream pipe length up to approximately 25 times pipe diameter, the required calibration factor decreases, then increases, and finally remains constant at lengths greater than 40 times pipe diameter. Eventually, a proper correction factor on the calibration curve was developed at different flow Reynolds numbers, for the first time, in order to modify the calibration curve at various upstream pipe lengths