Experimental Study of Hydraulic Performance of Stepped Spillway with a Curve Axis Affected by Downstream Channel Width Changes

Realization of the advantages of a higher degree of energy dissipation have created an increasing interest in stepped spillways. This study using a three dimensional, 1:50 scale, physical model was conducted to investigate the impact of variation downstream channel width of the converging stepped spillways with a curve axis. For this purpose, the converging stepped spillway with a curve axis was constructed and tested in four ratio of downstream channel width to spillway width ( ) ranging from 0.214 to 0.286. The results of the experiments indicated that in the converging steeped spillway by increasing total upstream head, the discharge coefficient will go up for each of the width ratio ( ) and before submergence stage for the spillway, the discharge coefficient is independent of downstream channel width variations. By contrast, when the spillway was submerged, there is a decrease in the coefficient of discharge can be caused by tailwater submergence and it causes the differences in the discharge coefficient for each of the widths ratio ( ). Also, the obtained data demonstrates that as increases, the flow depth and static pressure decreases at the bottom and the toe of the spillway model. Moreover, it was observed that as discharge increases, the energy dissipation decreases for all models, but model with higher ratio of lead to reduce more energy dissipation in higher discharge. In addition model with width ratio of due