Three-dimensional analysis of the performance of circular stepped spillways in the skimming flow regime

Abstract

By creating an artificial rough bed, stepped spillways increase energy dissipation during the spillway and reduce the risk of cavitation and the dimensions of the stilling basin. Combining stepped spillways with labyrinth spillways in order to improve their performance can be an attractive idea. Therefore, in this research, the hydraulic characteristics of the flow, the amount of energy dissipation and the residual energy of the flow downstream of the stepped spillway with a circular labyrinth configuration, with different numbers of cycles, were compared with the conventional stepped spillway. Validation of the numerical model was done using the results of the physical model. Four three-dimensional configurations of stepped spillway including: conventional stepped, two, three, and four-cycle circular labyrinth were modeled using OpenFOAM open source for the skimming flow regime. In order to simulate the flow, InterFOAM solver and RNG K-ԑ turbulence model were used. The results of the numerical model showed that the combination of the circular labyrinth with the stepped spillway causes an increase of 7.4, 28 and 18.3 percent of energy dissipation in circular forms of two, three and four cycles compared to its classical type for a constant discharge and yc/h=1.68. Therefore, among the circular labyrinth configurations, the three-cycle form (3CSS) has the highest dissipation rate. In addition, in the three-cycle circular labyrinth configuration, compared to other conventional and labyrinth configurations, it has resulted in less negative pressure in the upper half of the vertical face of the steps.