DISCHARGE EQUATION FOR SIMULTANEOUS FLOW OVER RECTANGULAR WEIRS AND BELOW INVERTED TRIANGULAR WEIRS

A combined weir consisting of a sharp-crested rectangular contracted w eir and an inverted triangular weir below is a now regulation device u sed in irrigation works for diverting the flow from a main channel to a secondary channel. The present practice for computing the discharge for classical rectangular and triangular weirs is from curves or equat ions relating the discharge coefficient and the upstream depth/gate op ening ratio parameter including weir geometry, and tailwater depth/gat e opening ratio being the fourth parameter which is needed to be updat ed. The discharge for simultaneous flow still in addition involves few more parameters: the distance between the weirs, the slope of the apr on, the opening depth and weir angle. In this paper one generalized eq uation including all the important variables is obtained from the expe rimental investigations. This equation is suitable for both horizontal and sloping channel bed under submerged flow and for the free flow, t he tailwater depth / weir opening ratio term being neglected. The pred ictions of the equation agreed well with the experimental data.