NUMERICAL AND EXPERIMENTAL ANALYSIS OF DIVIDING FLOW IN SHORT OPEN CHANNEL TRIBUTARIES

Abstract

Dividing flow in open channel junction is of interest in environmental and hydraulic engineering. It occurs in many hydraulic structures ranging from wastewater treatment facilities to fish passage conveyance structures, irrigation and drainage canals and natural river system. In this research, Schwarz-Christoffel transformation and principle of energy are used to predict the flow rates, the flow depths and values of Froude number in the tributary channels of rectangular open channel junction with three tributary channels. Also, an experimental program is performed to verify the numerical results of the theoretical solutions. The difficulty of a theoretical study of the dividing flow in an open channel due to the flow separation, recirculation regions and possibility of formation of hydraulic jump makes the complete numerical analysis of the problem impossible. However, in this study, with some particular assumptions to the problem, by adopting the conformal mapping technique (Schwarz – Christoffel transformation theory) and by applying the principle of conservation of energy, the flow pattern at a rectangular junction with three tributary channels is simulated; the numerical model is programmed on the computer with MATLAB Version 6.0.0.88 and the flow characteristics are evaluated. The verification of the results of the numerical model shows a will agreement between these results and those from the experimental model. The results revealed that: 1) Froude number in the main channel has negligible influence on the flow rates in the branches. 2) Flow characteristics in the main channel extension or in the branches depend largely on the geometrical dimensions of the junction. 3) The relative depths in the tributary channels independent of the junction geometry.