Experimental Study on Flow Measurement in Corrugated Metal Pipes Used in Irrigation Turnouts

Abstract

An innovative measurement system using submerged ultrasonic Doppler velocimetry (SUDV) has been adopted by the Lower Neches Valley Authority (LNVA) in Texas to measure flow velocity in corrugated metal pipes of an irrigation turnout. However, a 2% error in flow rate has been found due to the corrugation feature of the pipe. The objective of this study is to determine the correction coefficient by comparing the measured flow velocity with that measured using SUDV under full pipe flow conditions. The physical model is set up with inflow controlled by a sluice gate, passing through three chambers in series with two combinations of pipe sizes (61, 76, and 61 cm, and 91, 76, and 61 cm), which then flows through the last chamber and discharges water over a weir into a channel. Experimental results show an average velocity correction coefficient of .824 is satisfied for all pipe sizes evaluated in the experiment, with R2=.9898. The SUDVs in LNVA irrigation turnouts have been programmed with the correction coefficient to improve flow measurement accuracy for better water use management planning.