Research On Local Scour Around The Bridge Piers Using Numerical Simulations With Fluent And HEC-RAS Models

The scour that occurs around a bridge pier founded in erodible bed material is a complex three-dimensional phenomenon. The analysis and prediction of scour at bridges is complex. In this study, the relationships among field and numerical studies were investigated.Firstly, numerical modeling of two-phase model with a single cylindrical pier was simulated by three dimensional CFD module .Then, numerical modeling of four models which are one bridge from Myanmar and three bridges from United State of America, were modeled by one dimensional HEC-RAS module. Finally, the simulated results were compared with data from field observations and empirical scour prediction formulas by analytical methods.In 3-D simulation, scour prediction did not reach to the equilibrium condition because of the lack of CPU requirements .Change of velocity magnitudes and development of scour around pier were found reasonably. In 1-D simulation, reasonable agreement between field and model simulation outputs for velocity distribution and scour depth upstream of the bridge pier at four different field sites Simulated scour depths areclose to the HEC-18 and Froehlich (1988) formulas at low values of Fr₁, and while Fr₁continuously increases, the relative scour depths were among the values of HEC-18 and Froehlich (1991) formulas. Smaller sediment size relative to the pier width (larger valuesof b/d₅₀ ) can increase the scour process effectively in all studied cases.