Maximum energy loss in a vertical drop equipped with horizontal screen with downstream rough and smooth bed

Abstract

Screens are one of the recent energy dissipator structures that can be used downstream of small hydraulic structures. In this study, screens were used horizontally at the brinks of the vertical drop with downstream smooth and rough bed to investigate the energy loss of the drop. Experiments were performed on two porosities of screens, a relative critical depth of 0.13–0.39 and a median size of 1.9 cm aggregates. The results showed that for a relative critical depth of more than 0.3 in a vertical drop equipped with a screen with a rough bed, the drop length with respect to smooth bed increases. Compared to applying a Type I stilling basin, a vertical drop equipped with a screen with downstream smooth and rough bed reduces the drop length by approximately 50%. Although a rough bed increases air entrainment, it has no effect on the energy loss and pool depth of a vertical drop equipped with a horizontal screen with smooth bed. The use of horizontal screens at the brinks of the vertical drop causes maximum energy loss in the downstream of drop. Equations were provided to estimate the flow parameters with a R2 value of more than 0.925 and a normalized root mean square error of less than 0.04. HIGHLIGHTS Introducing a relatively new structure to create energy loss is presented.; The importance of energy loss in open channels flow is stated.; Using accurate laboratory results, the amount of energy loss in the channels has been investigated.; To understand the problem, proper hydraulic analysis is done.; The results of this research can be generalized in the design of hydraulic structures.;

Keywords

• energy loss
• rough and smooth bed
• screen
• vertical drop