Numerical Investigation of Velocity Profiles in Open Channels with Rough Bed

The velocity distribution is almost the most important argumentation in all of the open channel flows studies, since it is necessary for study of the mean and maximum velocities, estimation of discharge as well as for evaluation of shear stress on channel sides. The flow velocity distribution in a channel cross section depends on the shape of the section, the roughness of the channel, and the presence of the bends. So, it should be investigated before solving many of hydraulic problems in open channels. Characteristics of the roughness which mostly affect the flow are the size and shape of the roughness elements and spacing between them and also, the roughness concentration. In this study, velocity profiles in open channels with rough bed were investigated. FLUENT CFD package was used to implement the numerical method on the basis of the finite volume method. Results showed that the flow velocity along the canal increased over the rough bed. So, the shear stress, slope of the water surface and energy lose were increased in the flow direction. The skin friction coefficients were determined for different rough beds which were in good agreement with the numerical model values. As the number of roughness elements became more, their effects on velocity profiles were increased.