Hydraulics of free overfall in Δ-shaped channels

Abstract

In this paper, two methods are presented to analyse the free overfall in Δ-shaped (equilateral triangle-shaped) channels. First, the flow upstream of a free overfall from smooth horizontal or mildly sloping Δ-shaped channels is analysed theoretically to determine the end-depth-ratio (EDR), applying the momentum equation based on the Boussinesq approximation. Second, an alternate method for analysing free overfall in Δ-shaped channels is also presented where the flow over a free overfall in a Δ-shaped channel is simulated by that over a sharp-crested weir to calculate the EDR. The method of estimation of discharge from the known end depth is also presented for both the methods. These approaches eliminate the need of an experimentally determined pressure coefficient. Experiments are conducted to verify the results obtained from the present methods. Comparisons of the computed and experimental results are satisfactory.