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This study aims to evaluate the performance of proposed design for Bastora dam stepped spillway project. Experiments are conducted on a physical model, which is constructed at the laboratory of hydraulic engineering/ college of engineering/ Salahaddin University, Erbil-Iraq using an appropriate scale to avoid potential effects governing the model. The evaluation includes determining the flow regime passing the structure, length to and flow depth at the inception point, the efficiency of the structure to dissipate the energy at the toe, the height of side wall required for both the spillway chute and stilling basin at the downstream of the spillway and discharge coefficient. The results presented in the design report are compared with those measured/determined in this study and the design formulae of stepped spillway available in the literature. Although the comparisons show few discrepancies between the results, especially in terms of the energy dissipation rate and chute side wall dimension, the design report can be said acceptable and reliable.

The main features that attract hydraulic engineers for designing stepped spillways are their ability to lose a large portion of the flow energy and add or increase aeration to the flow naturally. Hence, smaller size stilling basin and no aeration device may require. This study aims to find the amount of energy dissipation rate and the location of inception point over non-uniform stepped spillway. The numerical 2D ANSYS-CFX code is applied to generate and run thirty-two models of different configurations using two different moderate slopes (1 V:2 H and 1 V:2.5 H) as most of the downstream slopes designed for moderate slope, and two different step heights (hs= 0.08 m and hs= 0.016 m) under skimming flow discharge for different (dc/hs) ranging from dc/hs= 1–2.2, in which dc is the critical flow deptho n the crest. The volume of fluid is implemented and the renormalized group of k-ɛ turbulence model is activated. The computational results demonstrated that the amount of energy dissipation increases with decreasing the flow discharge, chute slope, and step height. In addition, it is observed that the length of the inception point is directly proportional to the discharge and inversely proportional to both the chute slopes and step height. Moreover, for the design point of view, the results revealed that configuration B can be considered as the optimal one amongst the others examined herein.

Using stepped chutes as a structure for controlling flood discharges is applicable for long time. Measuring the depth of flow over that structure is essential for designing of the side walls. The aim of this paper is to determine the free-surface that flows on spillway equipped with non-uniform step sizes. For that purpose, the two-dimensional software package code of ANSYS-CFX has been utilized to run eight configurations of two moderate slopes (1V:2H and 1V:2.5H) and for four different discharges 1≤dc/hs≤2.2 to determine the effect of flow discharges, chute slopes, and step heights on the position of free surface along the structure over non-uniform stepped cascade. The hexahedral grid size of 0.015 m is selected with inflation technique close to the walls. In addition, the renormalized group of k-ε (RNG) turbulence model is implemented and the numerical volume of fluid software is employed. The results show smoother stream for higher discharges, and the free-surface drops when the slope of chutes increases. Moreover, it is found that the step size has insignificant effect on the depth of water. The results of this study are important because they provide new insight in improving the design of stepped spillways. It is recommended to perform more investigations to evaluate their effectiveness in other flow parameters including pressure distribution and energy dissipation rates.

This study is a numerical investigation in which a meshfree computational method known as the Smoothed Particle Hydrodynamics (SPH) is applied to examine its efficiency and accuracy in predicting the flow field variables of free surface flow passing a sluice gate. For this purpose, the numerical 2D SPHysics model, as an implementation of the computational SPH method, is adopted. The numerical code is validated against the theoretical and experimental results of previous works. The validation is performed taking into consideration the conjugate flow depths and velocities for different total upstream heads passing under a fixed gate opening height. The quantitative agreement between the results computed by the numerical 2D SPHysics code and the theoretical and experimental results is fairly good confirming that the numerical code is robust in predicting the flow properties in sluice gates. Then, the validated code is used to find the energy dissipation rate for various total upstream heads and Froude numbers. The results obtained in this study are promising, indicating that the numerical model can be considered as an efficient alternative tool for hydraulic engineers to predict and understand the flow behavior in hydraulic structures.