Numerical investigation of flow field and flowmeter accuracy in open-channel junctions

Abstract

The confluence of two natural rivers or two artificial channels is of special importance due to the complexity of flow behavior. Such complexity has considerable effects on the accuracy of flow characteristics measured by instruments. The main objective of this study is to investigate the effect of width and discharge ratio change on open-channel junction velocity distribution and flowmeter mean velocity measurement accuracy. To accomplish this, a CFD model of an open-channel junction was simulated and validated with an experimental study. After validation, the open-channel junction was modeled with various width and discharge ratios. The results showed that increasing the width ratio from W∗= 0.5 to W∗= 2.0 decreases the effect of tributary flow on main flow, which in turn results in a decrease in flowmeter measurement error from 73% to 35%, respectively. Also, the increment of discharge ratio from 0.25 to 0.75 reduces flowmeter measurement error from 59.5% to 13.65%.