Comparison of RANS, LES, and wind tunnel experiments for the calculation of wind loads on a low-rise building in its urban environment.

The majority of buildings are low-rise and their wind-resistant design plays an important role to reduce losses due to extreme wind events. Computational fluid dynamics is an attractive approach to study wind loads and offers high-resolution data output, but validation is required to assess its performance. The low-fidelity Reynolds-Averaged Navier-Stokes simulations offer fast calculations of the mean quantities and require additional empirical relationships to calculate turbulent statistics, such as the root-mean-square (rms) pressure coefficients (C_p). In contrast, the high-fidelity Large-eddy Simulations (LES) solve for the instantaneous fields allowing direct estimation of turbulent statistics. This study compares wind tunnel tests, RANS, and LES of a low-rise building in terms of mean, fluctuating, and peak C_p. The analysis considers 1) the isolated building and 2) the building in its urban environment, to evaluate the interference effects for different wind directions. Preliminary results for the most dominant wind direction show good agreement for the mean C_p, but RANS fails to predict rms C_p in regions of flow separation and recirculation of vortices at the building wakes. Future work will extend the comparison to turbulent statistics for all wind directions.