A sonar-based flow measurement technology for simultaneously measuring volumetric flow rate and volumetric percent of entrained air in paper and pulp slurries is described. The technology utilizes sonar array processing techniques to perform two independent measurements to characterize the process fluid. Firstly, the meter provides mixture volumetric flow by tracking the speed at which naturally occurring turbulent structures convect with the flow past an axial array sensors. The flow meter can be implemented either pressure transducers ported directly to the process fluid or with non-contact sensors clamped-on to existing process piping. Secondly, the meter utilizes the same sensors to determine the speed at which naturally occurring sound propagates through the process fluid. The speed of sound measurement provides an accurate and robust measurement of entrained air. Utilizing these two first principles based measurements, the sonar flow meter provides total mixture flow rate, while measuring and correcting for entrained air.

Data is presented that demonstrates the ability of the sonar meter to measure flow rates in single phase flows to within 0.5% accuracy for flows ranging from 3 to 20 ft/sec in a wide range of diameters. Calculations are presented demonstrating the link between entrained air and mixture sound speed indicating that the sonar meter can measure entrained air on a real time basis to an accuracy of better than 0.1% by volume.