Description
In open channels, the water flow is driven by gravity. In a long inclined prismatic channel, the flow will reach normal flow when there is an exact equilibrium between the gravity force component in the streamwise direction and the shear force. The water depth and velocity become independent of time and position at uniform equilibrium.
The momentum equation along a streamline states the exact balance between the shear forces and the gravity component. The normal flow conditions (i.e. uniform equilibrium flow properties) are deduced from the continuity and momentum equations. The calculations may require several iterations, depending upon the initial selection of a water depth. For turbulent flows, the Darcy-Weisbach factor may be estimated using the Colebrook-White formula or graphically from the Moody diagram.
Hubert Chanson.
