Varied Flow Functions for Circular Channels

Hydraulic engineers are often required to compute backwater curves and the existing methods cannot be applied accurately to closed conduits as the flow approaches the crown. This paper reviews the Keifer and Chu method which uses the dimensionless parameter Q/Q_cap. A new approach is developed to compute backwater curves in circular channels in which the factor Q/Q_cap is removed so that errors are not introduced by having to interpolate these values. This new method is applicable for all possible bed slope conditions (horizontal, adverse), which is a distinct advantage over the other existing techniques. Semigraphical methods are also suggested to increase the speed of computation of backwater curves.