experimental and numerical investigation of bridge configuration effect on hydraulic regime

The presence of a bridge structure in the river induces changes in the natural geometry of the river cross section by, therefore, altering the hydraulic regime significantly and causing the so-called backwater effect. nevertheless, the effect of the bridge configuration on the hydraulic regime is barely studied. therefore, the main objective of this study is to investigate the variations in the water surface profile and flow velocity due to the bridge structure configuration. for this purpose, the water surface profile and flow velocity on the upstream and downstream of the bridge were investigated for five flow discharges and four different bridge spans (m = b/b = 0.58, 0.67, 0.75, 0.83). in addition, the relationships between the bridge’s upstream and downstream average velocities were investigated. the analysis was carried out experimentally and numerically using the hec-ras model. the overall average velocity difference upstream of the bridge section was − 92.59%, while downstream of the bridge was determined as − 11.95%. so, the average velocities determined by hec-ras were considerably overestimated at the upstream part of the bridge. linear relationships were identified for the average downstream and upstream measured velocities in the different openings. the correlation coefficients (r2) were significantly high for considered for all tested b/b ratios. manning roughness coefficient n = 0.01 was found suitable for smooth open channel; nevertheless, a higher n value should be considered non-smooth open channel. the solution-oriented findings from this study might be helpful for engineers by assisting them to reduce uncertainties in the dimensioning of bridges structures