FLOW ANALYSIS IN SCOUR HOLE AROUND BRIDGE PIER USING ANSYS FLUENT

Abstract

The flow pattern around a bridge pier is complex to understand and the complexity increases with the development of a scour hole. As a result of scouring in piers , collapse of peirs in bridges can easily occur so it is very important to understand the variation of flow in and around the piers to take some factor of safety in constructing piers. In this study our aim is to simulate the flow around pier and to determine parameters such as shear stress,scour depth and velocity profiles. Flow is being simulated using different models. The models include mesh free models and mesh based models.They are made using RANS model (Reynolds Averaged Navier Stokes and continuity equations. Models are made in 3D and fine meshing of the models is being done to make comprehensive study. Models are also being made using SPH(smoothed particle hydrodynamics )for mesh free models .The equations used in this type of modelling are Lagrangian eqautions known as Navier Stokes equations. Similar geometric and kinematic conditions were created in ANSYS as used in laboratory experiment. The common conclusion is that both models predict a downflow near the upstream nose of the pier which would affect the stability of pier foundations. Velocity profiles from mesh free models and mesh based models at different locations are compared. They also help in obtaining significant knowledge regarding scouring of sediment in pier and particle approximation. Another new finding is the occurrence of flow separation and complex vortex stretching confined to the upper water column behind the pier. The predicted bed shear stress and turbulent kinetic energy are shown to compare well with the experimental data. Application of the mesh-free model to the flow in a scour hole around a bridge pier has been successful in generating desired approach flow. The results presented in this thesis are of practical values for prediction of sediment scour around bridge piers.