The Effect of Secondary Flow Strength on Bed Shear Stress around T-Shaped Spur Dike Locating in Various Positions of a 90 Degree

In this study, the effect of the secondary flow strength and vorticity on variations of bed shear stress for different positions of spur dike are compared through a mild 90˚ bend along with a T-shaped spur dike in a rigid bed. To carry out these experiments, three dimensional velocimeters (ADV) have been used for measuring velocity. Moreover, a comparison has been made between velocity vectors and variations of streamlines along the bend; the secondary flow strength and vorticity values are estimated for various positions of spur dike, and their effects on bed shear stress variations have been analyzed. It is concluded that the maximum secondary flow strength is evident in a distance of 0.6 of spur dike’s length at upstream under all these different positions of spur dike. Also the maximum vorticity position corresponds to the position of the maximum secondary flow strength, in front of spur dike’s wing. According to these results, it is predicted that the maximum scour occurs near the position of maximum secondary flow strength and maximum vorticity. Besides, the path of sediments motion coincides with the maximum shear stress points locus.