Effect of discharge ratio and stream angle on flow pattern at rectangular junction channels with fluent model

Open channel confluences occur in many natural and artificial waterways. Several hydraulic and geometric parameters such as discharge ratio، Froude number، junction angle، channel bed slope and bed roughness can affect flow pattern at channel junctions. Study of flow pattern in rigid boundary channels can help prediction of morphological changes in fluvial natural channels. In this research، the effect of discharge ratios and side channel junction angles on flow pattern for angles 30০، 45০، 60০ and 90০ using Fluent CFD model have been studied. Results showed that in =90০ junction angle، dimensions of separation zone disappear near bed (z*=0. 05) for discharge ratio of Q*=0. 917. Also in 45০،the dimensions of separation zone near bed are negligible. The maximum dimensions of separation zone are take place near water surface (z*=0. 95) for discharge ratio of Q*=0. 917 and 90০ degree junction channel. Increase in discharge ratio will lead to form uniform a flow downstream of junction area and so decrease in separation zone dimension. Also Maximum and minimum values (16% and 4%) of surface water level occur in highest and lowest discharge ratios of 0. 83 and 0. 917 respectively.