Experimental investigating on hydraulic parameters of vertical drop equipped with combined screens

In many overflow structures such as vertical drops, using the flow energy dissipator and investigating the subsequent effect on the hydraulic parameters are the most important issues in hydraulics. This study experimentally investigates the behavior of hydraulic parameters through the utilization of combined screens (horizontal-vertical) in vertical drops. The results revealed that the utilization of the screens combined with vertical drops reduces the relative mixing length and increases the relative pool depth and relative energy loss with respect to a simple vertical drop. It was also observed that the increase in the relative critical depth result in the increase in the relative wetted length of the vertical screens, the relative mixing length and the relative pool depth, and decrease in the relative energy loss. Evaluating the total energy dissipation of system by the effective components of energy dissipation exhibited that, by increasing relative critical depth, the performance of vertical drop equipped with horizontal screen decreases and the performance of vertical screen increases. However, the contribution of vertical drop equipped with a horizontal screen is more than 82% of the total energy loss of the system. Also, increasing the porosity of screen reduces the relative wetted length of horizontal and vertical screens, the relative mixing length and relative pool depth, and increase the relative energy loss.