Effect of Deflector and Aeration On the Discharge Coefficient of Submerged Flow of Morning Glory Spillways

Spillways are responsible for draining floods in dams. However, morning glory spillways are considered as free spillway type. In floods, a submerged flow is formed in their crest. This factor leads to severe pressure fluctuations in the shaft, suction and vibration of the structure and also reduces the spillway efficiency. Insufficient knowledge of the hydraulics of the submerged flow will be a warning sign for failure and overtopping of the dam. Studies show that the use of ancillary structures in morning glory spillways will improve the flow pattern. In this experimental research, an attempt has been made to investigate the effect of deflector and flow aeration by constructing a physical model and also the parameters affecting the discharge coefficient of submerged flow of morning glory spillways are expanded. Finally, by applying the weight effect of all geometric and hydraulic factors, a nonlinear relationship was introduced to estimate the discharge coefficient. The proposed relation with the RMSE of 0.091, compared to other previous relations (which have errors of 0.122 and 0.118) is able to better predict the discharge coefficient of submerged flow of spillway. The results also show that the discharge coefficient, unlike previous research, is highly dependent on the deflector.