THEORETICAL AND EXPERIMENTAL STUDY OF FLOW VELOCITY MEASUREMENT USING ULTRASONIC AND VORTEX FLOWMETER

Abstract

This study compares velocity measurements obtained from a clamp-on ultrasonic transit-time flowmeter and a vortex flowmeter. An electromagnetic flowmeter is used as the reference device. The theoretical flow velocity is determined from the regulated volumetric flow rate and the measuring tube diameter of each flowmeter. The analysis examines the deviation between calculated and measured velocities and the relationship between vortex-shedding frequency and flow velocity. Measurement uncertainty is defined in accordance with ISO/IEC Guide 98-3 (ISO-GUM). The experimental results demonstrate good agreement with the theoretical values within the range of expanded uncertainty. For the ultrasonic flowmeter, a largest deviation is observed at low velocities, reaching approximately −7%, where the small transit-time difference limits measurement resolution. At velocities above 0.4 m/s, corresponding to fully turbulent flow conditions, the measurements become more reliable. In contrast, the vortex flowmeter exhibits a different behavior. Once stable vortex shedding is established, at velocities above 1.4 m/s, the deviations are minimized with increasing velocity. The main differences between the flowmeters are primarily attributed to their underlying measurement principles rather than to systematic bias.