Investigating of Characteristics of Subcritical Flow in 90 Degrees Four-Branch Open Channel Junctions

One of the important parts of the urban and agriculture water conveyance systems are channel junctions. In this research، the effects of different factors such as inlet discharge ratio، bed elevation of lateral channels and height of weirs at the end of outlet channels on characteristics of the subcritical flow in 90 degrees four-branch open channel junctions with two inlets and two outlets were investigated experimentally. The results showed that as the inlet discharge ratio، bed elevation of lateral channels and height of weirs at the end of outlet channels increased، the outlet discharge in the main channel also increased. Increasing the inlet discharge ratio and decreasing the height of weirs at the end of outlet channels caused more fluctuation in the water surface profile at the junction، but variation of the bed elevation of lateral channels had no effect on fluctuations of the water surface profile. Furthermore، conjunction of the two inlet flows caused changing the velocity profiles in the inlet channels.