Numerical investigation of the influence of a hole at the pier of the bridge on the flow characteristics of the pier

The scour around the pier leads to bridge demolition. Therefore, the perception of the factors’ behavior affecting the scour and the capability to predict this phenomenon can offer important information to bridge designers. The development of a hole inside the pier is one the proposed solutions for reducing pier scour. In order to a better perception of the mechanism of hollow performance and its effect on the flow hydrodynamic around the pier, the numerical modeling of flow around the pier having a circular section with and without hollow is accomplished in rigid bed. The characteristics of the flow around the pier with and without the hollow are compared by the available laboratory information and using the 3 dimensional Flow3D model. The results showed that the development of hollow in pier leads to wider vortices after the pier and it is expected that the scour depth decreases around the pier. According to the results of this study, the turbulence energy and the bed shear stress can be reduced to 20% and 56%. Based on results of shear stress and comparing it with the critical shear stress, it is predicted that the amount of scouring around the pier when a hollow is developed can be reduced. Also, holes cause the less flow separation and returns flow after pier.