Impact of Angle of Converging Training Walls of Ogee-Spillway with a Curve Axis on Hydraulics Performance of Chute in Both Symmetrical and Asymmetrical Situations

The ogee spillway with a curve axis has a longer crest length than the spillway with linear crest. Therefore, in a specific reservoir water level, it can discharge higher flow rate compared to a straight one and due to this reason is preferred in applicable plans. In this study, physical model of Germi-Chai spillway which include an ogee crest with a curve axis and converging training walls was constructed in scale of 1:50. The SCWMRI Soil Conservation and Watershed Management Research Institute, has led a research effort on it. For each of the convergence angles, including 60 and 90 ̊ in both symmetrical and asymmetrical situations, flow characteristics such as discharge, water surfaces, depths and distributions of pressure were investigated in the downstream channel of the spillway. Experiments conducted in varying flow discharge from 30% to 177% of  design discharge. Based on visual observation, at the toe and the end of straight portions of the spillway face, due to converging training walls, interference streamlines occurred which led to generate a rooster tail phenomenon. It was observed that in the convergence angle of 90°, rooster tail had been witnessed up to slightly more than 118% Qd. However, it saw nearly 147% Qd in 60° convergences. Moreover, it should be emphasized that due to asymmetric angles, closest wall to the rooster tail had more static pressure.