Numerical Analysis of Flow Loading on Bluff Bodies

Today, Computational Fluid Dynamics (CFD) offers to engineers a promising way to understand, to test and to design large bridges. Several attempts have been made during the past ten years to introduce such techniques. The purpose of this paper is to present comparative results between numerical simulations and experimental measurements of the fluid loadings on three typical fixed or moving bluff bodies. The numerical approach is based on an efficient finite-element solver using an Arbitrary Lagrangian-Eulerian formulation for solving the two-dimensional incompressible Navier-Stokes equations with moving domains. Experimental tests consist of unsteady pressure measurements performed during sectional model tests. The Proper Orthogonal Decomposition applied to the wall pressure distributions is used in addition to spectral analyses in order to explain complex flow signature and motion-induced mechanisms. Effects of body shapes and dynamic characteristics (reduced wind speed, motion amplitude) on flow response and resulting loads are also examined. Those studies highlight that the direct resolution of the Navier-Stokes equations (with a laminar strategy without turbulence models) is sufficiently performing to reproduce the physics of the large vortex scales which dominate the signature and aeroelastic loadings, but can badly estimate reattachment areas and mean loading effects.