Aeroelastic Investigation of Long Span Suspension Bridge Decks by Numerical CFD and FSI Analyses

Abstract

CFD (Computational Fluid Dynamics) simulations appear to be strong competitor of the wind tunnel test which required scaled model and it is really expensive and time consuming tool in designing bridges therefore there is a strong claim to replace them with CFD. Analyses carried out for different deck cross sections by secondary development of commercial computational fluid dynamics software ANSYS FLUENT, establishing two dimensional bending and torsional fluid-structure interaction (FSI) numerical model to calculate flutter critical wind speed. The flutter motion belongs to a sharp growth of amplitude (heave or rotation) as a function of the wind speed can be detected by performing the FSI at different wind speeds set in FLUENT model as a velocity inlet. By using the two neighboring wind speeds the critical wind speed can be obtained once a decay motion oscillation observed. Steady and unsteady simulations have been computed in order to judge the feasibility of CFD simulations in the early design stage of long span bridges. Additionally realizable (κ-ε) model with enhanced wall treatment and (κ-ω SST) turbulence models have been considered to verify their performance in bridge aerodynamics problems. It has been found that static aerodynamic coefficients have been correctly modeled using a steady simulation, while flutter critical wind speed is judged from time histories of unsteady simulations for stationary deck sections. The validity of the simulation method was verified by comparison of simulation results with the work done by other researchers.

Keywords: CFD, critical flutter wind speed, bridge aeroelasticity, suspension bridges.