Development of a Direct Explicit Equation for Hydraulic Design of Semi-elliptical Channels

One of the common concrete channels in irrigation networks is the semielliptical prefabricated channels. Manning formula is usually used to design these channels. The cross-sectional area and the wetted perimeter are required to be calculated in Manning formula. There are no analytical solutions to directly compute these parameters. Thus, numerical integration methods are inevitably used. In this paper, a wide number of various semielliptical channels are regarded and their cross-sectional areas and wetted perimeters for different depths were computed numerically to produce databases for three-dimensional curve fitting. Direct relationships for the cross-sectional area and the wetted perimeter in terms of the channels size and the hydraulic parameters were developed. These relationships were used in the design of the semielliptical concrete channels and the results were compared with the numerical ones. The results were quite close to each other which indicates that the developed direct relationships are appropriate for design purposes of semielliptical prefabricated channels.