CFD simulation of the wind environment around an isolated high-rise building: An evaluation of SRANS, LES and DES models

• Performances of SRANS, LES and DES modeling approaches are compared in simulating airflow around a building.
• Effects of discretization time step and sampling time are analyzed.
• DES can produce results similar as LES with lower mesh numbers and lower computing time.
• Instantaneous wind flow features around a building can be obtained from DES.
• DES is demonstrated in saving computational time and hardware requirements.

The choice of proper turbulence models in computational fluid dynamics is still a challenging issue for accurately predicting outdoor microclimate and thermal comfort conditions in urban planning. This study compared the performances of the Steady Reynolds Averaged Navier–Stokes (SRANS) RNG k-ε, Large Eddy Simulation (LES) and Detached Eddy Simulation (DES) modeling approaches in simulating the wind flow around an isolated building (with a 1:1:2 shape). The effects of the computational parameters were analyzed, including the grid resolution for all cases, and the discretization time step (Δt) and non-dimensional sampling time (t*) for the LES and DES cases. The results of the LES and DES simulations were affected by the gradual decrease in Δt and increase in t* until the two parameters reached 0.005 s and 288, respectively. The mean velocity fields on the windward side of the building predicted by the three models were in good agreement with the wind tunnel results. However, the results of the LES and DES cases were in better agreement with the experimental results for the leeward and lateral regions in both vertical and horizontal planes. The DDES (Delayed Detached Eddy Simulation) and LES models predicted similar results in the wake region, but the DDES has a lower overall mesh requirement. It is encouraging that the DDES model provides not only the mean flow field, but also the instantaneous wind characteristics, which can be useful for more accurate analysis of outdoor wind and thermal comfort.