Optimum location and performance of submerged vanes to control scour depth at river confluence

The location where two rivers are joint، is defined as river channel confluence. Due to three dimensional flow structure at channel confluence especially on the downstream mixing of flow، a deep scour hole is developed. At the separation zone downstream of junction corner، a point bar is developed. The scour hole and point bar can cause change in river morphology and can be the main reason for bank instability or failure of the structures near the confluence area. Submerged vanes are those structures which have been developed to control bank erosion. These vanes also have been used to prevent sediment to enter the intakes. However the submerged vanes have not been studied to control scour depth at the river confluence، therefore it is the main purpose of this study to conduct experimental tests to determine the best location and the optimum size and performance of vanes for the purpose of controlling scour at river confluence. To reach the objective of this study، an extensive experimental study was conducted in the hydraulic laboratory of Shahid Chamran University. Tests were conducted in three series of A، B، and C. In series of A the best location was found. In series of B the best hydraulic performance was found and in series of C the best dimensions of vanes were obtained. From the experimental results، it was found that the best location of the submerged vanes is the downstream left bank of the lateral channel. The vane should be installed at angle of 30 degree. Relations for the height، width and spacing of the vanes are presented.