Numerical simulation of dispersion around an isolated cubic building: Comparison of various types of k–ɛ models

Prediction accuracy of flow and dispersion around a cubic building with a flush vent located on its roof was examined using various k–ɛ models, and numerical results were compared with wind-tunnel data. Four types of turbulence models, i.e., the standard k–ɛ model, the RNG k–ɛ model, the k–ɛ model with Launder and Kato modification and the Realizable k–ɛ model were compared in this study. The standard k–ɛ model provided inadequate results for the concentration field, because it could not reproduce the basic flow structure, such as the reverse flow on the roof. However, revised k–ɛ models provided concentrations in better agreement with the experimental data. The effect of an oblique wind angle and vent locations on the prediction accuracy was also investigated. It was confirmed that the prediction accuracy of the velocity field strongly affected that of the concentration field. The RNG model showed general agreement with the experiment, and was the best of the turbulence models tested. However, it becomes clear that the results for all CFD models show poor prediction accuracy of concentration distribution at the side and leeward surfaces of the building since they all underestimate the concentration diffusion on these regions. The concentrations predicted by all CFD models were less diffusive than those of the experiment.