numerical analysis of obstacle placement on stepped spillway and its impact on energy dissipation

In the present study, the effect of the placement of continuous obstacles with different heights on the edge of steps of a stepped spillway with eight steps, a slope of 1v:1.9h, and in the skimming flow regime was simulated. the results show that the presence of an obstacle on the spillway edge introduces changes in the flow structure. in the absence of an obstacle, the flow velocity distribution pattern across the spillway was relatively uniform, with the maximum velocity observed at the edge of the downstream steps. however changes in the velocity profiles at the cross-sections were observed. the presence of the obstacles led to an increase in the flow velocity at the location of the obstacle in the flow field, and this increase in velocity was amplified with an increase in the obstacle height. furthermore, the results indicate that the presence of the obstacle results in a reduction in the turbulent kinetic energy of the flow. this reduction was more significant with an increase in the obstacle height. the reduction in turbulent kinetic energy due to the presence of the obstacle may lead to a decrease in energy dissipation compared to the case without obstacles. in summary, the combined effect of the relative increase in the flow velocity and the decrease in the turbulent kinetic energy in the models with an obstacle is introduced as the effective factor for the lack of improvement in energy dissipation compared to the model without an obstacle.