Effect of Fluid Density and Temperature on Discharge Coefficient of Ogee Spillways Using Physical Models

Spillways are constructed to allow excess flood safely to downstream of a dam. In any dams spillways are used for passing of water flow that exceeds the designed capacity. Most of the dams fail due to insufficient spillway capacity or inappropriate design. Spillways are structures, used for measuring water pass of canals and many other applications. Hence lots of efforts have been made in increasing accuracy of flow measurement of such structures. The structure of the Spillway is a major problem in fixing the type of spillway and its design for construction of dam. Taking into account appropriate discharge coefficient and investigation of spillway for long term hydraulic performance plot are understood to be important. Spillways are of the most important structure, upper limit of the curved is designed in a way that it will be closer to lower profile of water pass which is ventilated on a sharp crest and is in appropriate with water pass. Preventing ventilation under the water pass, there is a contact between spilled water and spillway head profile. This work presents suitable graphs for selection and supply based on type of fluid flowing on the spillways as the key elements to use this type of spillways in construction of dams. To do this, physical-hydraulic model and observed Power Industry performed measurement tests and hydraulic parameters were analyzed and discharge coefficient in different fields including surface roughness in Ogee spillway model were studied. Increase of density and temperature of water over spillway the discharge coefficient decreases. Also from experiments results it is found that for different discharges, with the increase in density decrees the performance and increase in temperature decreases the performance.