The Application of Numerical Method and SKM Quasi-Two-Dimensional Model to Estimate the Shear Stress around a Cylindrical Pier with Submerged Vanes

Investigation of the shear stress to estimate the scour hole around bridge piers is of utmost importance, but a review of the literature shows that the study of this factor, around protected piers by various methods of scour control has not been studied by the researchers. In this research, a three dimensional numerical model has been used to study the variation shear stress on the bridge pier with submerged vanes. However, due to difficulty of calculating the amount of shear stress in the wild, researchers provided indirect ways to calculate these parameters that one of these methods, is the use of quasi-two-dimensional model Shino and Knight (SKM In this study, the pattern of shear stress distribution around the base with a different number of vanes (2, 4 & 6), with the two angle of the flow (20 and 30 degree) and in flow intensity 0.95 (critical flow intensity), with both methods were studied and compared. Both model results show that vanes placement has a great effect on reducing velocity of the passing flow and thus decreasing the bed shear stress around the pier. Also analysis of the counts and placement angles showed that 6 vanes rather to 2 and 4 vanes and also angle of 30 degree rather to angle of 20 degree performs better in action, so that the shear stress reduces the amount of 12-15 percent.