Experimental Investigation of the Performance of Inclined Gabion Drop Equipped with a Horizontal Screen

One of the important hydraulic issues is to study the effect of additional structures on dissipating the flow energy in overflow structures such as drops. In the present study, using a laboratory model, the effect of simultaneous use of horizontal screen and gabion in the inclined drop structure was investigated and compared with the results of other researchers. The experiments were performed for two heights and three inclined gabion angles, two screen porosity ratios and a flow rate of 150 to 800 liters per minute. The results of all the studied models showed that by increasing the relative critical depth, the relative energy consumption values decrease and the relative downstream depth increases. By increasing angle and height of the slope and decreasing the porosity of the screen for a constant relative critical depth, the relative energy dissipation of the inclined gabion drops equipped with a horizontal screen increases. Increasing the wetted length of horizontal screens causes two-phase flow and air entrance to the used system and consequently the amount of energy dissipation increases. Simultaneous use of gabions in the sloping section and horizontal screens at the edge of the drop has significantly reduced the downstream Froude number so that the downstream Froude number at all three angles and two porosity ratios decreased from range of 4.49-35 to range of 1.31-2.48 compared to the simple inclined slope and from range of 1.48-5.78 to range of 1.31-2.48 as compared to the inclined slope equipped with a horizontal lattice plate.