عنوان مقاله [English]
In the stepped spillway, the steps, by providing an artificial roughening bed, dissipate the flow of energy more than other types of spillways, which reduce the time and cost of constriction the dam and have been able to attract the designer's attention to these types of spillways. But what is important in this type of spillway, increasing the effectiveness of steps in the rate of energy dissipation. For this reason, the present study intends to consider the addition of wedge-shaped elements on the steps and its impact on the variation of the Darcy roughness, the height of the downstream water flow and, as a result, energy depletion on the stepped spillway. In this regard, first, several shapes of wedge elements are simulated with different layouts using Flow-3D software and then by comparing the results, the proper model from aspect the most energy dissipation has been studied in the laboratory. Experiments were performed on 5 physical models, with changes in wedge layout and discharge rate, and the results were compared with simple stepped spillway. Numerical and experimental results show that the addition of wedge elements on the steps increases the Darcy roughness coefficient and reduces the height of water in the downstream of the spillway and as a result, the energy depletion increases significantly. By reducing the distance between the wedge elements, energy depreciation increases more significantly. Also, there are relationships between the Darcy roughness (f) and the ratio of the critical depth to the step roughness of the stairs (yc / k), that the high accuracy of these relationships (R2 = 0.9-0.98) indicate a significant dependence of the Darcy roughness (f) to the step roughness (k).