Negin Binesh - Ph.D Student, Water Resources Engineering, Faculty of Environment, University of Tehran, Tehran, Iran
Hossein Bonakdari - Associate Professor, Department of Civil Engineering, Razi University, Kermanshah, Iran

In this study, velocity profiles by different mathematical models are compared with a proposed semi-analytical equation for predicting longitudinal velocity distribution in outer region of narrow open channels, using data from a real site of a sewer network located in France. Also the ability of the models in predicting dip phenomenon (a situation where maximum velocity occurs below the water surface) is discussed. The results show that all models are capable of describing the velocity profiles and velocity negative gradient near the free surface; but the semi-analytical proposed model offers the best results compared to the measured data and provides the least errors, and is capable of predicting the position of maximum velocity below the water surface very well.

sewer, open channel, velocity distribution, dip phenomenon