Ziqiang He

Gas flowmeters are a key reference for natural gas trade settlement. To advance on-site verification technology, this paper presents air and natural gas flow test systems employing a clamp-on gas ultrasonic flowmeter, and systematically investigates the effects of pipeline parameters, pressure conditions, transducer usage, and noise reflection on measurement accuracy. Quantitative results show that measurement errors can be controlled within ±2% by selecting appropriate transducer types and installing them beyond 20D downstream of disturbances. Moreover, the proposed dual-transducer synchronous measurement—using two sets of transducers at the same location in different acoustic directions and averaging the results—effectively suppresses radial velocity effects, reducing installation and flow-related errors to within ±1.5%. Installing a single layer of acoustic damping material (≥30 mm beyond the transducer) further improves the coherent signal-to-noise ratio above 30 dB, ensuring reliable performance under noisy conditions. These quantitative findings offer practical guidelines for on-site calibration of natural gas flowmeters, contributing to improved fairness in gas trade measurement.

Flow-induced vibration of a semi-circular cylinder has been simulated to investigate the influence of cut angle ([ ]) and degree of freedom. The turbulent flow has been applied to the stream in the simulation. It’s shown that the rise of [ ] can enlarge the amplitude both in and perpendicular to flow directions, the peak value of amplitude in cross-flow direction is obtained 2.53D ([ ], flat forebodies). The lock-in regime can be captured in most cases. In addition, the high value of [ ] also results in a high time-averaged drag coefficient. The wake structures transition corresponds to the vibration model transform by changing the hydrodynamic force acting on the cylinder. Furthermore, the 2S pattern, 2S[ ] pattern, 2P pattern, [ ] pattern, and [ ] pattern can be observed in this work.