Mirali Mohammadi - Department of Civil Engineering, Faculty of Engineering, The University of Urmia,

Spatially varied flow in open channels occurs in a large variety of hydraulic structures as well as road/bridge surface drainage channels. The equation of motion for spatially variable flow in an open channel, being produced by the lateral or a vertical inflow, has been treated previously. However, these are not applicable to the phenomenon of runoff from a plane surface, which is an example of spatially varied flow. This paper reviews the state of the subject and presents the experimental data applying a practical equation of motion mathematically derived. Several series of experiments are carried out in a vshaped bottom channel. These experiments are used to model specific rainfall intensity and discharge. For this particular channel shape, longitudinal water surface profiles are plotted and are compared with the profiles given by the equation of motion treated for this channel shape. Analysis of the results agrees well with the experimental data and the proposed equation for supercritical flows. The results, however, show that the profiles slope does not normally increase as the flow discharge increases at the end of the channel. This result confirms that the flow resistance in spatially varied flow as well as the critical depth position along the channel and cross sectional shape should be taken into account.

spatially varied flow, hydraulic structures, water surface profiles, flow resistance, cross sectional shape