Investigation of Flow Pattern around Rectangular and Oblong Piers with collar Located in a 180o Sharp Bend

Abstract

12 Flow in river bends is associated with generation of secondary flows that leads to a rather 13 complicated flow pattern around bridge piers located in the bend. In this study, the flow patterns 14 around rectangular and oblong piers models with collar located at the 90 angle of a 180-degree 15 sharp bend in an experimental plume were investigated. The 3D flow velocity data were 16 collected using a Vectrino velocimeter. The experimental results indicated that the presence of 17 the rectangular pier caused more intense deviation of the streamlines towards the outer bank of 18 the bend. Furthermore, installation of the oblong pier, the maximum secondary flow power and 19 angular velocity were decreased, respectively, by 35% and 45% in comparison with the 20 installation of the rectangular pier. In addition, it was found that the maximum turbulence 21 kinetic energy around the two piers was not significantly different, but by installing the 22 rectangular pier, a region with high values of turbulence kinetic energy is formed at 90° near 23 the inner bank. Also, installation of oblong pier reduces the values of shear stress in comparison 24 with the use of the rectangular pier. 25