Optimization of bend flow characteristics using multi-objective evaluation and numerical simulation

Rough-strip energy dissipators (R-SEDs) are commonly used as auxiliary engineering measures due to their simple designs and ease of construction. R-SEDs at the bottom of curved drainage channels can achieve flow diversion and velocity reduction. This study comprehensively selected six arrangement parameters affecting the effect of R-SED flow diversion and velocity reduction (i.e., angle θ, height ratio λ, relative height h, spacing s, thickness δ, and length L of R-SEDs). Six-factor three-level orthogonal tests were performed. A multi-criteria evaluation system was developed with the coefficients of variation of water surface transverse slope (CW) and the coefficients of variation of average flow velocity (CV) as the sub-evaluation indexes and the combined weighting coefficient (SS) as the combined evaluation index. In addition, R-SED arrangement parameters were optimized. The results show that the importance of factors affecting flow diversion, velocity reduction, and overall effects of R-SEDs were ranked in descending order: θ > λ > δ > L > h > s, h > L > θ > δ > λ > s, and h > θ > L > δ > λ > s, respectively. The preferred R-SED arrangement was as follows: h = 0.4, λ = 1.0, s = 5 m, θ = 60°, δ = (1/10)w, and L = 0.2w. Under the preferred combination, R-SEDs achieved better overall flow diversion and velocity reduction performance. CV (0.501) decreased by 29.54% and 18.93% compared with those under no R-SED and the optimum condition in the orthogonal test (run 9), respectively. CW (0.285) decreased by 47.12% and 8.37% compared with those under no R-SED and run 9, respectively. SS (0.959) was 107.58% and 11.12% higher than those under no R-SED and run 9, respectively. The findings can provide insights for studying bend flow energy dissipators.