Investigation of flow patterns around rectangular and oblong piers with collar located in a 180-degree sharp bend

Flow in river bends is associated with generation of secondary flows that leads to a rather complicated flow pattern around bridge piers located in the bend. In this study, the flow patterns around rectangular and oblong piers models with collar located at the 90o angle of a 180-degree sharp bend in an experimental plume were investigated. The 3D flow velocity data were collected using a Vectrino velocimeter. The experimental results indicated that the presence of the rectangular pier caused more intense deviation of the streamlines towards the outer bank of the bend. Furthermore, installation of the oblong pier, the maximum secondary flow power and angular velocity were decreased, respectively, by 35% and 45% in comparison with the installation of the rectangular pier. In addition, it was found that the maximum turbulence kinetic energy around the two piers was not significantly different, but by installing the rectangular pier, a region with high values of turbulence kinetic energy is formed at 90° near the inner bank. Also, installation of oblong pier reduces the values of shear stress in comparison with the use of the rectangular pier.