Experimentally determination of discharge coefficients of Ogee spillway under axial arc condition with convergent lateral walls

A dam spillway is a hydraulic structure that appropriately and safely diverts the outflow to downstream, so that the dam stability and passing of flood flows can be guaranteed. Compared to straight crest spillway, an Ogee spillway with curvature in plan in a fixed-width can pass more flow. Therefore under the low hydraulic heads and the need for a smaller place in plane, they are considered as an economical structure so that their application from several aspects are under developed. An experimental model of the Garmi-Chay Miane dam spillway was made in 1:50 scale. The water head over spillway crest was measured in the eight discharges values and consequently the efficiency of spillway were determined. For Q/Qd ranging from 0.63-1.13, discharge coefficient had ascendant trend with acceptable agreement against the diagram of USBR, while for Q/Qd between 1.13-1.51, due to the submergence of spillway, the discharge coefficient decreased.