Numerical and experimental analysis of flow distortion induced by ultrasonic transducers in gas flowmeters

This study investigates the flow field distribution near the transducer and quantifies the distortion of the velocity profile along ultrasonic paths. It elucidates the physical mechanisms through which flow separation—induced by the mainstream flow around the transducer—affects ultrasonic flowmeter measurements. Experimental analyses examine the influence of localized flow field distortion under various pressures and flow rates, leading to the development of an error correction model consistent with empirical data. Numerical simulations are performed for three transducer installation modes: fully projecting, fully recessed, and tangent, revealing the distinct physical mechanisms associated with each configuration. Measurement errors are consistently negative due to the effects of backflow and lateral flow. Error ranges are − 1.86% to -1.15% for fully projecting, -4.09% to -2.26% for tangent, and − 10.57% to -9.66% for fully recessed installations, indicating that the fully recessed mode introduces the most significant flow disturbance. Flow velocity correction models are proposed for each installation type. After modification, errors are largely confined within ± 1.0% for both fully projecting and fully recessed transducers. The effect of local flow distortion on tangent-type ultrasonic flowmeters is further examined through experiments under varying pressures and flow velocities. By applying a secondary correction model based on Reynolds number, measurement accuracy can achieve the ± 0.5% standard.