抄録
Study for accurate flowrate measurement for complicated flow like just after double bent is examined using Ultrasonic Velocity Profile (UVP) method. The characteristics of velocity profiles from the radial measurement lines to the center of pipe are investigated to form the three-dimensional sound field measurement system to obtain accurate flowrate. Multiple transducers and radial measurement lines are necessary to reproduce three-dimensional velocity profiles of complicated flow. In the case of measurements just after simple double bent, flowrate measurement about 3% error is realized using three transducers at the distance of as short as 3 D in the condition of Re~40,000. However, another analytical optimization study for number of transducers and distance from the bent is also executed adopting sampling theory and signal analytical method using FFT. 36 measured velocity profiles are accumulated to obtain velocity profiles along circumferential measuring circles, and Fourier amplitude of those velocity profiles along the measuring circles suggest the largest wave number for each distance. Analytical optimal number for transducer for each distance is given from the results. Both experimental optimizations are confirmed by numerical method using CFD code.
