Quality assessment of Large-Eddy Simulation of wind flow around a high-rise building : validation and solution verification

When undertaking wind engineering problems such as urban pollutant dispersion or pedestrian wind comfort with Computational Fluid Dynamics,an accurate simulation of the flow-field around buildings is required. In this respect, the good performance of Large-Eddy Simulation has already been established but because the formulation and the use of this turbulence modeling approach are complex, the uncertainty on the results is relatively high.This implies the need for Validation and Verification(V&V)studies like the one performed inthe present paper for the wind flow around an isolated high-rise build ing with aspec tratio 1:1:2. In the first part of the study , the numerical results are compared with measurements from a reference wind-tunnel experiment and the agreement is quantified by validation metrics. The vortex method to generate in flow turbulence is shown to provide accurate results. Unexpectedly, the best agreement with the experiments isobtained on the coarsest computatio nal grid, with 20 cells per building side, while afinergrid with 30cells per building side overstimates the turbulent kinetic energy measurements. A similar result was also found by earlier studies for different flow configurations. In the second part of the study, solution verificationis performed. The Systematic Grid and Model Variation technique isused to provide estimates of the modeling and numerical error contributions.The LES_IQindicatorshows that a grid with 20(resp.30)cells per building side allows resolving 80%(resp.91%)ofthe total turbulent kinetic energy in the region around the building.2013 Elsevier Ltd.All rights reserved