Iranian Journal of Irrigation & Drainage

Iranian Journal of Irrigation & Drainage

Numerical Study of Flow Field and Turbulence in a Compound Channel with Diverging Floodplain with Vegetation

Document Type : Original Article

Authors
1 Department of water engineering, Lorestan University, Khoramabad, Iran
2 Department of Water Engineering, Lorestan University, Khorramabad, Iran.
3 Department of civil engineering, Islamic Azad University, BuinZahra Branch, BuinZahra, Iran.
Abstract
Vegetation in the flood plains is effective on the turbulent flow of compound channels, especially in flood conditions where the flow depth changes. Numerical simulation is very useful in investigating the effect of vegetation on turbulent flow. In the present study, the numerical simulation of the flow in the diverging floodplain of compound channel in two cases with and without vegetation at different relative depths has been done using the Flow3D numerical model. The results showed that the flow velocity in the main channel is always higher than that of floodplain. The collision of the flow with the vegetation has led to a decrease in the velocity in floodplain compared to the state without vegetation. Investigation of turbulence parameters showed that the highest value of shear velocity occurred at the common border of the main channel and the floodplain, but with the increase in relative depth, the value of shear velocity and shear stress decreased. Also, at a fixed relative depth, the turbulence intensity is the highest near the walls and the lowest in the middle parts of the main channel. The investigation of the downstream of the divergence area showed that in the case of vegetation, the turbulence intensity is the highest in the center line of the floodplain channel and near the free surface, while in the absence of vegetation, the highest turbulence intensity occurred near the bottom of the floodplain.
Keywords

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