Assessment of RANS turbulence models in urban environments: CFD simulation of airflow around idealized high-rise morphologies.

This study presents the evaluation of Reynolds-averaged Navier Stokes (RANS) turbulence models, including the RNG k − ε, SST k − ω and more recently developed SST γ − Reθ models of flow past an idealized three-dimensional urban canopy. For validation purposes, the simulated vertical and spanwise profiles of mean velocity are compared with wind tunnel measurements and large eddy simulation (LES) results. These quantitative validations are essential to assess the accuracy of RANS turbulence models for the simulation of flow in built environments. Furthermore, additional CFD simulations are performed to determine the influence of three different idealized high-rise morphologies on the flow within and above the semi-idealized urban canopy. In order to assess airflow behavior, the pressure coefficient on high-rise morphologies, turbulence kinetic energy contours and vertical velocity magnitude profiles at roof level of high-rise and surrounding buildings are evaluated. The results render the SST γ − Reθ model attractive and useful for the simulation of flows in real and complex urban morphologies. For the region around an idealized high-rise building, different flow patterns and strong changes in velocity magnitude and pressure coefficient are observed for different building morphologies.