Velocity Distribution Model in Open Channels Based on the Harmonic Mean Distance.

Document Type : Research Studies

Authors

1 Irrigation and Hydraulics Engineering Department., Faculty of Engineering., El-Mansoura University., Mansoura., Egypt.

2 Irrigation and Hydraulics Department., El-Mansoura University., Faculty of Engineering., Mansoura., Egypt.

3 Irrigation and Hydraulics Department., Faculty of Engineering., El-Mansoura University., Mansoura., Egypt.

Abstract

A new analytical technique for drawing isovel patterns in any open channel cross section is presented based on the Harmonic Mean Distance concept. It is assumed that the instantaneous velocity at a point in the section is affected by the roughness of each point in the boundary and its distance from it. A computer program is established to compute the Harmonic Mean Distance at all points for open channel of different cross sections, taking into consideration the effect of the free surface and the composite roughness. Based on the Harmonic Mean Distance the 2-D velocity distribution is predicted using the power law distribution and the logarithmic distribution. Also the velocity factors (α and β ), the location of the maximum velocity, and the ratio of the maximum to the mean velocity (Umccx / V) are calculated. The proposed model is verified with measured velocity profiles from a previous work of other researchers on rectangular cross sections and showed good agreement. 

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