Subcritical Flow Computation in an Open-Channel Network with Dividing Junctions and Sluice Gates

Abstract

This study focuses on the development of an integrated analytical-numerical solver to model subcritical open channel flows in a channel network, which includes dividing channel junctions, flow through a sluice gate, and gradually varied flow transition between gate and gate, or gate and junction. The fundamental equations describing flows in a channel junction and a sluice gate of a trapezoidal cross section are derived. The flow rates and corresponding water depths in each branch channel for various cases of given discharges in the upstream main channel and the geometric features of the main channel and the branch channels are computed. The correlation of water depths between upstream and downstream of a control gate for water flows through it is also investigated. The gate opening for a needed flow rate can be determined. The predicted water depths and flow rates for a channel junction with a 90 branch channel are compared to the published analytical and experimental results. Good agreements have been achieved, where the averaged relative percentage error at main channel extension and branch channel are 7.57 % and 4.23 %, respectively. Additionally, the predicted water depths at downstream of the main trapezoidal channel in general are less than those with the cases of a rectangular channel junction. However, the water depths at a branch channel are greater than those in a dividing channel junction of rectangular section. In contrast, flow rates at the downstream main trapezoidal channel and branch channel are respectively greater and less than the values obtained in a channel junction of rectangular section.