The purpose of the work is firstly to explore the proposal from a previous North Sea Flow Measurement Workshop paper that increasing the number of chordal locations above 4 yields little improvement in the performance of ultrasonic flow meters. Secondly the work examines the relationship between profile factor and symmetry on theoretical velocity profiles and how that changes with an increased number of chordal locations. Finally, the benefits of more paths for the purposes of swirl cancellation are reviewed, particularly when axial asymmetry and swirl are present concurrently. It is found that in the presence of axial asymmetry there is a significant performance improvement to be had with an increased number of chordal locations. A relationship between profile factor and error is also apparent. The interpolation polynomial and weight function are used to visualize the quadrature and explain the correlation. The theory that more chordal locations will improve the correlation between error and profile factor is investigated, however initial results suggest this is not true. The theory behind swirl cancellation is explained and the velocity profile diagnostics of common designs in the presence of swirl and axial asymmetry are shown. Examples of how the user can be fooled into thinking all is well in the presence of both axial asymmetry and swirl are also shown. The sensitivity of some designs to swirl is also examined. The modelling suggests that in cases where swirl and axial asymmetry are present together and non-axial velocity components are not removed by swirl cancellation or flow conditioners, a change in traditional velocity profile diagnostics cannot be used to indicate the magnitude of the error.
ARNOULD, P. 2020. An investigation into the performance and diagnostics from different chordal integration schemes in asymmetric flow. Flow measurement and instrumentation [online], 72, article ID 101644. Available from: https://doi.org/10.1016/j.flowmeasinst.2019.101644