Effect of low-frequency ultrasound on flow rate measurements using the ultrasonic velocity profile method

Abstract

This study presents a low-frequency ultrasonic propagation analysis using the finite-element method (FEM). Experimental results of flow rate measurements using the ultrasonic velocity profile (UVP) method are also presented. The ultrasound frequency, pipe diameter, and pipe wall thickness are 0.274 MHz, 590.6 mm, and 9.5 mm, respectively. Six waves are generated per ultrasound pulse. To analyze the entire pipe region, the FEM is combined with the Kirchhoff method. The experiments of flow rate measurements are conducted using the high Reynolds number calibration facility at the National Metrology Institute of Japan. The range of the Reynolds number is from 4.4×106 to 1.7×107. Wide spreading of the ultrasonic beam in the axial direction of the pipe is observed because of multiple reflections in the pipe wall. This wide beam affects the measured velocity profile, particularly in the region near the pipe wall. In addition, the flow rate errors are approximately 10% (deviating by 1.1%) across the investigated range of Reynolds number. This result suggests that the experimental flow rate errors might be used as correction factors of flow rate measurements using the UVP method.