محمد واقفی

Bridges are among the most vital and critical hydraulic structures being used since long time ago, and local scour around bridge piers is one of factors contributing in instability and eventually failure of bridges. Hence, it is of high importance to propose methods of controlling and reducing this phenomenon. Various methods have been proposed to prevent and reduce local scour around bridge piers. Using submerged vanes is one of the methods in which researchers are interested. Submerged vanes are thin rectangular structures which is created high pressure and low pressure zones on two sides due to having a streamwise angle. These structures cause generation of the secondary vortex and variation in flow pattern at river bed, and consequently a shift in the process of sediment transport and scour. The flow pattern and velocity variations in the vicinity of the bridge pier and the submerged vanes presented in a straight channel are complicated and three dimensional, they will be even more complicated when the bridge pier and submerged vanes are installed in a bended channel considering the flow pattern in the bends. Therefore, this study conducts an experimental and numerical investigation of scour around a bridge pier and the effect of submerged vanes on reduction of scour around the bridge pier installed in a 180 degree sharp bend. To this aim, the submerged vanes were placed at the upstream side of the pier in order to study the effect of different distances of overlap lengths between the vanes, the position of the vanes at channel width, the distance of the vanes from the center of the bridge pier, and the distance of the vanes from each other on reduction of scour depth around the bridge pier. The results of the present study indicated that, among all of the arrangements, the maximum scour reduction occurred with 100% overlapped vanes located at a distance of 2.5 times pier diameter from the pier and a distance of 1 times pier diameter from each other, which led t