Abstract:

An experimental hydraulic model investigation was conducted to evaluate the performance of a stepped overflow spillway . The spillway tested has a standard ogee profile with continuous steps cut into a straight portion of downstream face from tangential point (P.T) to the toe . Five constant dimensions (h/l=1.4) steps were used . The objectives of the study are to evaluate the effectiveness of steps on the amount of energy loss under nappe , transision and skimming flow regime . A preliminary comparison with a standard spillway (WES) , that the average increase in energy dissipation at toe is approximately 37% , that would imply a significant reduction of the size of downstream stilling basins . The experimental results indicate that dissipation is highest for the small values of yc/Nh tested (i.e at nappe to transition flow) , also the dissipation ratio increase with increasing N . However , the results are compared to the earlier investigation , for commonly used ranges of the steps and flow condition a general relation is established between the energy loss and the parameter yc/Nh , which may be useful as a predictive formula in a practical applications .

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