Numerical and experimental study of pitched steps effects in stepped spillway on the hydraulic parameters and energy dissipation in the skimming flow

One of the most prominent features of the stepped spillway performance is the considerable loss of energy during it compared with other types of spillway. Considering this feature, obtaining a more detailed view on the energy dissipation parameter and, finally, increasing its amount has been the focus of most studies related to this type of spillway. For this purpose, using a Flow-3D model, the effect of pitched steps (steps with hole) on the velocity and pressure variations, water height at downstream and energy dissipation has been investigated. As well as the appropriate model of the most energy dissipation in the laboratory was developed and studied. Numerical and experimental results show that pitched steps reduces the velocity to about (82-69%) and reduces the water height at the downstream by up to 33%, and the energy dissipation is increased to about 4 times. According to the pressure distribution profiles at the vertical edge of the step, it was observed that the amount of negative pressure in the vertical wall decreased by about 82%, and the positive pressure was approximately increased by 3 and 4 times. The negative pressure on the floor of the steps is turned into positive and the positive pressure near the edge is increased due to the presence of the hole. Also, the results showed that the error rate of the studied parameters in the numerical and experimental models was very low and acceptable, indicating a good fit between numerical and experimental data.