CFD Simulation of Open Channel Flooding Flows and Scouring Around Bridge Structures

Simulation of scour-pit formations under the bridge decks and around the bridge piers, due to sediment suspension and transport caused by flooding and pressure flow conditions, is of significant interest nowadays to computational fluid dynamics (CFD) and hydraulic researchers. From CFD perspective, analysis of bridge under various flooding conditions and impact of the drag and lift forces on it, are necessary to determine bridge stability. This study is focused on the simulation of open channel turbulent flows over inundated bridge deck and evolution of scour pit under various flooding conditions. Solutions for flow field and turbulence, using a representative bed roughness value, are based on Reynolds Averaged Navier-Stokes (RANS) equations, and turbulence closure model using a commercial CFD code. An iterative computational methodology is developed for the evolution of scour-pit profile using the single-phase slip-flat-top surface with (re)moving boundary formulation, based on an empirical correlation for critical shear stress to characterize initiation of sediment removal. The computational model has demonstrated stable and converged solution for the evolution of the scour-pit shape and size using a constant critical shear stress value. The success of the simulation model can be substantially improved with development of a functional critical shear stress by taking into account solid-fluid interactions, scour bed profile and slope, as well as more extensive validation with experimental data. Key-Words: Bridge structures, CFD simulation, Computational fluid dynamics, Flooding flows, Flow scouring, Turbulence modeling.