Engineering and Technology Journal

This study was adopted a new concept to enhance performance of stepped spillway towards more dissipation of kinetic energy along chute face through increases interlocking surface areas between the mainstream and trapping cavity recirculation vortices on the tread of chute steps and each step edge that beneath it, and increasing the interaction of the flow interference over stepped spillway. The aim of this concept is by employment the specification of a labyrinth weir by configured as a stepped spillway, to produce new steps named as Labyrinth stepped spillway. Experiments were restricted in skimming flow regimes, it have been carried out on four physical models with chute angles (35°). Where models are classified into three labyrinth stepped spillway models of three different magnification length ratios LT/W=1.1, 1.2, and 1.3, additionally; a traditional or conventional shape models were used for comparison. All physical models assembled with step height 4 cm, eight steps constructed for a total height of 32 cm and width of 30 cm .The results generally show that the energy dissipation with labyrinth shape stepped spillway was more than resulted with the traditional shape. As the magnification ratio increase, the energy dissipation observed to increase compare with traditional model.

A suggested design of Bastora stepped spillway has been taken as a prototype to build a physical wooden model with scale of 1:20 (Lm/Lp). Experiments have been carried out on the model with slope of upward inclined steps of 420, 280, 140 and 00. For every slope of the steps, experiments were conducted in three flow regimes, nappe, transition, and skimming. As observed in experiments, the increase in the slope of steps has no significant effect on the flow behaviour over stepped spillway. The hydraulic depths of flow over the model were measured and the energy dissipation rate was calculated. Results show that the energy dissipation decreases with increasing the discharge, and the energy dissipation of flow on stepped spillways with upward inclined
steps is more than on the horizontal stepped spillways, it increases with increasing the adverse slope of steps.