Benchmark on the Aerodynamics of a Rectangular Cylinder: sensitivity to inflow conditions

This thesis deals with the numerical simulation of the international benchmark on the aerodynamics of a sharp-edged rectangular cylinder with a chord-to-depth ratio equal to 5. In spite of its simple geometry, this benchmark can shed new light in the fundamentals of the aerodynamic behavior of a wide range of actual bluff bodies, such as bridges or high-rise buildings. The aim of this thesis is, in particular, to investigate the sensitivity of the numerical results to the inlet conditions, namely to the free-stream incidence, the inlet turbulence length and intensity. Indeed, the numerical and experimental data collected in the benchmark show a large dispersion as far as the flow behavior on the cylinder side is concerned and the reasons of this dispersion are not yet fully understood. The sensitivity to inflow conditions is of great interest also for future experimental studies, in which the inlet flow conditions cannot be perfectly known. To this aim, unsteady RANS simulations have been carried out by using two different turbulence models and the commercial code Fluent. The SST k-w and the Reynolds stress turbulence models are considered. The Reynolds number, based on the free-stream velocity and the cylinder depth, is 40000. 25 simulations are performed for each turbulence model by varying the three considered parameters. These simulations are repeated for two different grids, a fine one, for which grid independence of the results has been checked, and a coarser one. This might also give an idea of the effects of numerical discretization errors compared to those of the considered inlet parameters and of turbulence modeling. The results are also compared with previous data in the literature There is a general good agreement between the outputs of the two turbulence models and with the previous experimental data for all the bulk parameters. The main differences, which however fall within the range described in literature, concern the time fluctuations of the lift coefficient and the flow behavior on the cylinder side. Regarding the sensitivity to inflow conditions, we can say that the main parameter that affects the results in terms of aerodynamic forces (mean and rms) and of the pressure field is the incidence, while turbulence length and intensity have a minor effect