Performance evaluation by computational fluid dynamics modelling of the heavy gas dispersion with a low Froude number in a built environment

摘要

To evaluate the dispersion of a heavy gas, such as sulphur hexafluoride, with a low Froude number in a built environment, an experimental and numerical simulation study was conducted. The experiment was carried out using seven different injection inlet configurations in an experimental chamber. The release rate was found to have a great effect on the concentration in the lower part of the chamber. The obstacle in the middle of the chamber could cause a non-uniform distribution of concentration, particularly due to variations in locations and angles of the release outlets. Additionally, numerical simulations were carried out to evaluate four turbulence models: the standard k-epsilon model, the realizable k-epsilon model, the re-normalization group (RNG) k-epsilon model and the shear stress transport (SST) k-omega model. Four indicators were used to evaluate the turbulent model performance. In general, the SST k-omega model performed the best, with geometric mean bias (MG) = 0.968 and geometric variance (VG) = 1.09 at 0.055 m height, and with MG = 0.384 and VG = 2.80 at 0.6 m height. The standard k-epsilon model was the next best in performance, followed by the realizable k-epsilon and the RNG k-epsilon model.