محمد واقفی

Local scour is considered as one of the reasons of instability and ultimately failure of bridges. In order to protect bridges against serious scour damage, various control strategies have been presented. One of the common methods to control erosion and modify bed sediment transport regime is using submerged vanes. For this purpose, in this study, at first, the flow pattern and scour pattern around the bridge pier with the submerged vanes located at pier's upstream in sharp bend laboratory flume is studied. Subsequently, bed topography changes and flow pattern in the bend with the presence of bridge pier and submerged vanes were investigated using SSIIM software. The flum that was used has 180 degree bend and the ratio beetwen the central radius and channel width is 2. In 27 experiments, the effect of various parameters of submerged vanes, including the number, length and angle have been investigated on the control of scouring around a pier located at 90 degree of bend. In the SSIIM software, at first the validation of scour pattern in three models and flow pattern in one model was performed. Then, in 54 modeling, the effect of the parameters of submerged plates on the upstream of pier, which located at 60 and 120 degrees, has been investigated. The results of this study show that in experimental models, the presence of submerged vanes in the upstream of bridge pier located at 90 degrees has a significant effect on reducing the scour depth around the pier than the bridge pier experiment. In all experiments, the maximum scour depth around the pier with the presence of submerged vanes in comparison with the single bridge pier test has decreased. The maximum percentage reduction of scour depth around bridge pier occurred for the case when three submerged vanes with length of 1.5 times pier diameter and angle of 15 degree were used, which its amount is 30%. The results of the analysis of the flow pattern in the bend indicate that the maximum velocity at the beginning of