| 摘要 |
A fluid flow measurement arrangement is disclosed where the effects of high-order acoustic modes are suppressed in ultrasonic flow measurement. Ultrasonic transducers (2, 3) are arranged in a duct (4, 13) configured to carry a fluid. Ultrasonic signals between the transducers (2, 3) travel in a plurality of high order modes having velocities slower than a fundamental mode whose time of flight is desired to be determined with accuracy. A measurement portion between the transducers is adapted to suppress the effects of the non-fundamental modes, notably to suppress their propagation. Embodiments disclosed to achieve this suppression include inserting fluid dynamically configured obstructions (10; 11, 12) (fig. 6, Fig. 7) within the measurement portion, and/or making the cross section of the measurement portion non-uniform (Figs. 15A, 15B). |
