Applicability of URANS and DES simulations of flow past rectangular cylinders and bridge sections

This paper discusses the results of computational fluid dynamics simulations carried out for rectangular cylinders with various side ratios of interest for many civil engineering structures. A bridge deck of common cross-section geometry was also considered. Unsteady Reynolds-averaged Navier-Stokes (URANS) equations were solved in conjunction with either an eddy-viscosity or a linearized explicit algebraic Reynolds stress model. The analysis showed that for the case studies considered the 2-D URANS approach was able to give reasonable results if coupled with an advanced turbulence model and a suitable computational mesh. The simulations even reproduced, at least qualitatively, complex phenomena observed in the wind tunnel, such as Reynolds-number effects for a sharp-edged geometry. The study focused both on stationary and harmonically oscillating bodies. For the latter, self-excited forces and flutter derivatives were calculated and compared to experimental data. In the particular case of a benchmark rectangular 5:1 cylinder, 3-D detached-eddy simulations were also carried out, highlighting the improvement in the accuracy of the results with respect to both 2-D and 3-D URANS calculations. All the computations were performed with the DLR-Tau Code, a non-commercial unstructured solver developed by the German Aerospace Center.