Evaluation of Energy Dissipation and Hydraulic Characteristics of Flow on Simple and Inclined Stepped Spillways using FLUENT Model

Stepped spillways are hydraulic structures which due to the high energy loss of flow have important role in reducing dimensions of stilling basin of downstream of the dams and consequently their economical design. The dam designers tended to study the characteristics of flow on this type of spillways in recent decades. Horizontal steps, inclined steps, and steps with end sills may be used in stepped spillways. The energy loss of flow on stepped chute depends on the total discharge per unit width of chute, the total flow head, the step height, the step length, the gravitational acceleration, and the height characteristics of the step. For the inclined step, the height characteristics is the increment of step above the horizontal level or the angles of step.
The objective of the study is to compare the relative energy dissipation between horizontal steps and inclined steps and find the optimal energy dissipation efficiency for flow on stepped chutes. In this paper, the effect of angles of inclined step, relative critical depth, and relative discharge on the relative energy dissipation over stepped spillways are investigated and discussed, too. To achieve this goal, first the FLUENT model’s output results for simulation of flow passing over a stepped spillway are validated using the experimental data, and then effect of the of angles of inclined step is examined. Also, an equation for the estimate of the relative energy dissipation for inclined stepped spillways was developed.