Computational Fluid Dynamics Simulation of Open-Channel Flows Over Bridge-Decks Under Various Flooding Conditions

The bridge ‘hydraulics analysis and design’ could be substantially enhanced using advanced commercial Computational Fluid Dynamics (CFD) software and powerful parallel computing resources. The objective of the present study is to validate STAR-CD commercial CFD software for the bridge hydraulics research. This study simulates limited scaled experimental data conducted elsewhere for bridge flooding in open channel flow with Froude number, Fr=0.22, and dimensionless inundation height ration, h*=1.5. Two approaches are used to simulate two-dimensional open channel turbulent flow with six different turbulence models. The first approach uses transient VOF methodology for two-phase, open channel free surface, and the other approach uses steady state method with free surface as a fixed slip-flat-top wall. Drag and lift coefficients are computed and compared with limited experimental data. The transient VOF simulations, which are found to be slow, unstable and over-sensitive to its computational parameters, result in larger discrepancies for drag and lift coefficients than the second, steadystate method with the fixed slip-flat-top wall, the latter gives faster, more stable solutions than transient VOF simulations, and shows better agreement with available experimental results. The k-ε Renormalization Group (RNG) is identified as the best turbulence model for our simulation, still predicting 27 % higher drag coefficient than limited experimental results with unknown accuracy. Further improvements can be done using the non-linear eddy viscosity turbulence models or Large Eddy Simulation (LES), as well as three-dimensional computational models with more realistic boundary conditions and more optimized simulation parameters. Key-Words:-Bridge deck, CFD simulation, Computational fluid dynamics, Flooding flows, Turbulence modeling,