Ultrasonic water measurement in irrigation pipelines with disturbed flow

Ultrasonicflow meter accuracy was investigated over a range of flow conditions (3 pipe materials, 2 pipe sizes, 4 Reynolds numbers, 7 flow-disturbing devices) commonly found in irrigation systems. Flow rate measurements were taken at five locations downstream from a flow disturbance. The measurement accuracy was within +/-5% of actual flow at a minimum of 10 pipe diameters downstream from the flow disturbances. Errors as high as 36.5% occurred when measurements were taken close to some flow disturbances. A multiplier was developed to correct for directional bias for devices that fell into the Group I category (single elbow, two elbows, check valve, and 50% open butterfly valve with vertical and horizontal orientation). Applying the multiplier at 4.5 pipe diameters and higher resulted in accuracies within +/-4% of actual flow. The regression analysis performed on Group I devices showed that the USFM performance was not significantly different for the three pipe materials, two pipe diameters, and four flow rates.