A New Relationship Between the Coefficient Of Manning and of Rugosity Ks for Use in Ac-W Equation for Uniform Flow in Artificial and Natural Channels

This communication deals with how to obtaining a relationship between the roughness coefficients n of the Manning`s equation and Colebrook-White`s Ks (CW) to be used in an equation called AC-W for uniform flow in natural and artificial channels. The AC-W equation was adapted from the CW which, in turn, is suitable for pressurized flow in pipes. The expression AC-W has been producing better results than the Manning equation for uniform flow experimental data because it has a correction term to contemplate the shape effects of the open channel section. The main question for the use of the AC-W expression is the determination of the roughness Ks that does not have methodology consolidated yet. Thus, it is reported how the relationship between the Manning coefficient n and the roughness Ks for use in the AC-W equation has been obtained, based on experimental data of uniform flow in triangular, circular and natural channels. It was also demonstrated the superiority of the AC-W equation compared to Manning`s in the calculation of the flow in the studied channels.