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, which leads to the development of a rather complicated ow pattern around bridge piers located in the bend. The present study investigated the ow patterns around models for rectangular and oblong piers with a collar located at the 90-degree angle of a 180-degree sharp bend in an experimental plume. The 3D ow velocity data were collected using a Vectrino velocimeter. The experimental results indicated that the presence of the rectangular pier caused a more intense deviation of the streamlines towards the outer bank of the bend. Furthermore, installation of the oblong pier, rather than the rectangular pier, decreased the maximum secondary ow power and angular velocity by 35% and 45%, respectively. It was also found that the maximum turbulence kinetic energy around the two piers was not significantly different; however, by installing the rectangular pier, a region with high values of turbulence kinetic energy was formed at 90O near the inner bank. Moreover, installation of the oblong pier could reduce shear stress.