The R-SED has both energy dissipation and flow diversion effects on the bend flow, and the influencing factors affecting these effects are generally divided into R-SED layout parameters (such as relative height of R-SED, height ratio of R-SED, R-SED spacing, R-SED angle and R-SED thickness) and curved spillway engineering parameters (such as centerline radius of the bend, bend width, bend angle and bottom slope of the bend). The simple shape and convenient construction of R-SEDs can effectively solve the adverse hydraulic phenomena in the curved spillway, which will facilitate the safe and stable operation of the curved spillway and the continuous downstream water supply (such as industrial and irrigation water). Thus, in this paper, a simpler rough-strip energy dissipator (R-SED) was added to the bend of curved spillways. However, compared with the research on the basic characteristics of bend flow, the research on related engineering measures is still rare. Based on the understanding of the basic bend flow characteristics, scholars have improved the bend flow pattern using engineering measures such as permeable spurs ( Yang et al. 2013 Seyedashraf & Akhtari 2015 Engel & Rhoads 2016 Gu et al. 2020) and secondary flow evolution ( Booij 2003 Huai et al. 2011 Seyedashraf & Akhtari 2015 Vaghefi et al. 2017 Maatooq & Hameed 2020), flow velocity distribution ( Han et al. The study of the basic characteristics of the bend flow is focused on the water depth distribution ( Seyedashraf & Akhtari 2015 Zhang et al. The research on bend flow is mainly divided into the study of basic water flow characteristics and the study of engineering measures to improve the flow pattern of bend flow. Currently, various research methods of bend flow have been developed, mainly including model tests, numerical simulations and theoretical studies. In 1876, Thomson (1876) first proposed the problem of bend circulating flow through experimental research. The bend flow is one of the topics in the field of hydraulics research.

Relative height of R-SED and bend angle were significant factors affecting energy dissipation effects height ratio of R-SED and centerline radius of the bend were significant factors affecting flow diversion effects the coefficient of variation of superelevation had a larger weight (0.549) than the energy dissipation rate (0.451), indicating that R-SEDs' flow diversion effects were larger than their energy dissipation effects height ratio of R-SED, centerline radius of the bend and bend angle were significant factors affecting overall energy dissipation and flow diversion effects and selected as key factors for further steepest climbing tests and response surface design. Influencing factors (i.e., relative height, height ratio, spacing, angle and thickness of R-SEDs as well as centerline radius, width, angle and bottom slope of the bend) of R-SEDs' energy dissipation and flow diversion effects were analyzed using Minitab 21.1 in combination with the entropy weight method and the TOPSIS method.

Energy dissipation rate and coefficient of variation of superelevation were used as evaluation indices. In this paper, twelve Plackett-Burman tests were conducted. Rough-strip energy dissipators (R-SEDs) at the bottom of spillway bends have energy dissipation and flow diversion effects on bend flow.

Concrete flume with energy dissipators