Inflow condition sensitivity in the CFD simulation of wind flow in the urban environment.

Wind flow modeling in urban areas is influenced by many uncertainties, such as geometric detailing, inflow and boundary conditions, numerical approach (RANS, LES, and DNS) and turbulence model. This study aims to investigate how the different inflow conditions that are usually adopted to simulate urban wind flows may affect the accuracy of the results. CFD simulations were performed on a selected urban area - “Quartiere La Venezia” in Livorno (Italy) - using a steady-state RANS approach. Wind tunnel tests performed on the same urban model were used as a benchmark to validate the numerical simulations. In particular, two types of inflow profiles for the same wind direction were considered, corresponding to the wind tunnel measures and the logarithmic approximation, respectively. Mean wind profiles at 25 locations were compared and the statistical performance in terms of four different metrics was quantified for both inflow conditions. The results show that slightly different inflow conditions can greatly affect the results in terms of mean wind speed and turbulent kinetic energy.