RANS Simulation of Incompressible Flow Around Bridge Sections

The Computational Fluid Dynamics is an active research field in civil engineering and the simulation of the flow around bluff bodies is often used as a supplement to wind-tunnel experiments for the structural design of buildings, towers and above all bridges. These very complex flows are characterized by massive separation zones, unstable shear layers, reattachments and shedding of large eddies. The goal of the present research work is the simulation of low Mach number incompressible flows around bluff bodies using the DLR-Tau code. Moreover the possibility of using 2D Unsteady Reynolds Averaged Navier-Stokes Simulations (URANS) instead of the much more cumbersome 3D Large Eddy Simulations (LES), which are often considered the only reasonable approach, is investigated with first encouraging results. First, the capability of Tau code to simulate low Mach number flows is successfully checked by comparison with experiments available for a NACA 0012 airfoil. Then, in order to deal in the future with complex bridge deck geometries, the flow around simpler bluff bodies such as rectangular cylinders is computed. In particular a square cylinder and a rectangular cylinder with chord-to-thickness ratio of 5.0 are chosen as first study cases, since a wide range of reliable experimental and numerical results are available in literature for comparison. The influence of both numerical parameters (turbulence model, spatial and temporal discretisation) and flow parameters (Reynolds number, angle-of-attack) is investigated. The agreement with experiments and available LES simulations is generally good, especially as regards integral quantities such as aerodynamic force coefficients and Strouhal number