Experimental Investigation of Horseshoe-Shaped Spillway Hydraulics and Effect of Spillway Length on Discharge Coefficient

One of the non-linear weirs is horseshoe-shaped weir that determination of its hydraulic parameters for designing of that is necessary. Sometime due to limitation in dam site and also reduction in soil excavation volume, tunnel and intake location of hydro-electric power this structure is needed to be constructed near the dam and its intake. In these cases, a combined structure of both the intake and spillway can be constructed by using horseshoe-shaped weir to achieve a proper economic condition in dam construction. In this study, by making physical models of the horseshoeshaped spillway in laboratory dimension, some hydraulic parameters like discharge coefficient, velocity and water surface profiles in different parts of the horseshoe-shaped spillway were investigated. Results showed that in horseshoe-shaped spillways, with increasing the ratio of head to spillway length, discharge coefficient was decreased about 0.6 to 0.7. This reduction in discharge coefficient had different trends for spillways with length of greater or less than 112cm. Comparison of the results between the rectangular weir and the horseshoe-shaped spillway by consideration an equal width for them showed that horseshoe-shaped spillway could reduce head above the weir about 54%. Investigation of the water surface profiles showed that overflowing of waters into the horseshoe spillway, created the rooster tail type hydraulic jump.