مهندسی منابع آب (Feb 2016)
Comparison of Erosion and Sedimentation Patterns Facilitated by a Spur Dike and a Triangular-Shaped Vane Structures in a 90° Mild Bend under the Influence of Different Froude Numbers
Abstract
Spur dikes and triangular-shaped vanes are structures that control the erosion of a river’s outer bend by the diversion of flow from there to its center. In this study, the erosion and sedimentation patterns around a spur dike and a triangular-shaped vane was investigated using an experimental model with a 90-degree mild bend. The triangular-shaped vane and spur dike with an effective length of one-fifth of the width of the canal (14 cm) and under different hydraulic conditions (Froude numbers 0.194, 0.214, 0.233 and 0.253) were tested. In all tests, a single triangular-shaped vane with an angle of 30 degree to the upstream direction, and a spur dike with an angle of 90 degree were installed in the outer bank of a flume in a 72° position, where the maximum scour depth usually occurs. For all tests, flow depth was kept constant equal to 13 cm. Bed topography was measured at the end of each experiment and the geometry of scour hole and point bar were determined. The results show that the maximum scour depth of the spur dike structure was more than that of the triangular-shaped vane. The average of maximum scour depth of the triangular-shaped vane and spur dike were 0.55 and 1.0 times that of the structure effective length, respectively. In addition, the maximum scour depth distance from the outer bank with a triangular-shaped vane was more than of the spur dike. The average distance of the maximum scour depth of spur dike and triangular-shaped vane structures from the outer bank were1.0 and 1.4 times the effective length of the structure, respectively. The point bar distance from the outer bank the spur dike structure was more for the triangular-shaped vane. The average point bar distance from the outer bank for spur dike and triangular-shaped vane were 0.34 and 0.1 times of effective length of the structure, respectively.
