Experimental and steady-RANS CFD modelling of cross-ventilation in moderately-dense urban areas

Computational fluid dynamics (CFD) models based on the steady Reynolds-averaged Navier Stokes (SRANS) equations are vastly used for calculation of airflow field inside and around cross-ventilated buildings. However, most of the developed CFD guidelines neglect CFD challenges related to cross-ventilation modeling in terms of flow unsteadiness, high level of gradients of airflow parameters, and complex interactions between the indoor and outdoor flows. Hence, a systematic parametric study was performed in this study for a generic cross-ventilated building model with a planar area ratio of 0.25 against different wind angles while effects of different CFD parameters, including advection and diffusion terms’ discretization methods, mesh generation techniques, and turbulence models on prediction accuracy and convergence behavior of CFD solver were comprehensively studied. Results show that a particularly generated unstructured tetrahedral mesh configuration with significantly lower cell numbers can provide comparable results with structured hexahedral mesh configurations. Furthermore, the second-order discretization scheme for the advection terms encounters convergence issues against the normal wind angle, but generally presents more accurate results against oblique wind angles. Moreover, two-equation turbulence models show a very low accuracy in the case of the normal wind angle, but acceptable results can be found for oblique wind angles.