The flow pattern in triangular channels along the side weir for subcritical flow regime

• The 3D flow pattern within triangular channel along a side weir is simulated.
• The turbulent RNG k–ε model was used to simulate turbulent flow field.
• The volume of fluid (VOF) scheme was applied to simulate free surface variations.

Side weirs in triangular channels are used for control and measurement of flow in irrigation networks and drainage systems. The main purpose of this study is investigation of the effects of side weirs on the subcritical flow conditions parameters in the triangular channels that is not 3D simulated numerically, so far. The turbulent RNG k−εk−ε model and the volume of fluid (VOF) scheme were used to simulate turbulent flow field and flow free surface in a triangular channel along the side weir, respectively. Comparison of numerical and experimental results shows that the numerical model simulates the free surface and flow field characteristics with acceptable accuracy. First, the flow pattern within triangular channel along the side weir in subcritical flow regime is investigated numerically. Due to the side weir inlet effects, a sudden drop occurred at the first quarter of the side weir length. Then, the effects of subcritical regime Froude numbers in range of 0.406–0.793 are investigated. At all the Froude numbers, a surface jump occurred along the end quarter of the weir length. The length of this surface jump increased with increasing the Froude number. The angle of spilling jet pattern (φφ) was similar for all the Froude numbers. However, the minimum φφ decreased upon increasing Froude number. For all the Froude numbers, a secondary flow cell was produced after the side weir, which developed as it moved downstream in the main channel.