Mohammad Sarfaraz - Graduate Student, Department of Civil Engineering, Sharif University of Technology, Iran
Jalal Attari - Assistant Professor, Power and Water University of Technology, Iran
Michael Pfister - Ph.D., Laboratory of Hydraulic Constructions (LCH), Ecole Polytechnique Fédérale de Lausanne

Stepped spillways have gained much interest in recent decades because of their compatibility with Roller Compacted Concrete (RCC) dams. Hydraulics of stepped spillways is not simple considering different flow regimes and regions along the chute. Estimation of flow characteristics of the stepped chutes is presently carried out by using some empirical formulae and physical modeling, which are partially inaccurate if scaled up due to scale effects produced by high interaction between air and water. However, this can be improved by application of Computational Fluid Dynamics (CFD) models. The inception point of aeration of stepped spillways is placed further upstream than on smooth spillways. The position of this point is relevant to cavitation potential, flow losses and flow depth; hence an accurate approximation of the inception point location is essential. In this paper, flow characteristics with emphasis of investigating air concentration in a stepped spillway having a steep slope, was computed by a commercial CFD program. A comparison of the numerical and physical model results showed a relatively good agreement. The study indicates that the turbulence numerical simulation is an effective and useful method for the complex stepped spillway overflow

Stepped Spillway, Air Entrainment, Inception Point, Numerical Modeling, Large Eddy Simulation