Investigation of Velocity Changes in a Straight Asymmetric Rectangular Composite Channel Using Flow-3D Software

In this study, the flow inside a rectangular composite channel was studied by finite volume numerical method, for which Flow-3d software was used. Comparing the results of the numerical model with the laboratory results, it was concluded that the numerical model can well simulate the flow inside a rectangular composite channel. Performing numerical modeling of suitable boundary conditions, a grid with the desired dimensions and a suitable turbulence model was obtained to describe the hydraulic flow inside the rectangular composite channel. Three turbulence models of the two equations K-ε, RNG K-ε and K-ω and one turbulence model of large vortices LES were used. Also, the effect of geometric parameters and flow on the average velocity in the composite channel was investigated. The results obtained from this study show that with increasing the width of the floodplain at different depths, the flow velocity has decreased, so that in the value of = 0.75 (yf / H), with decreasing the flood width of the right plain from 5.71 to 13.33 cm, the ratio of flow velocity in the section of the main channel to the average velocity has also increased by 51%. It should be noted that with increasing the depth of the floodplain, the flow velocity has decreased. Also, with increasing the height of the main channel wall, the flow velocity decreases.