Large-scale forcing effects on wind flows in the urban canopy: impact of inflow conditions

Wind flow modeling in urban areas is usually performed by means of Wind-Tunnel (WT) testing or Computational Fluid Dynamics (CFD) simulations. Results obtained with both techniques can be affected by the boundary conditions. This study aims at investigating how two sets of inflow conditions, termed set 1 and set 2 and calculated respectively using the equations proposed by Richards and Hoxey (1993) and Tominaga et al. (2008), may affect the accuracy of the results in terms of mean wind speed, turbulent kinetic energy, yaw and pitch angles when predicting wind flows in urban areas. 3D steady RANS simulations were performed for a selected urban area (“Quartiere La Venezia” in Livorno, Italy). WT tests on the same urban model were used to validate the CFD simulations. Mean wind profiles at 25 positions in the urban area were compared and the statistical performance was quantified using four metrics for both sets of inflow conditions. The results obtained using the two sets of inflow conditions showed comparable performances in terms of wind flow predictions in the urban canopy, which means that at the building scale there is no need to use more accurate conditions because they are as effective as the simpler ones.