INFLUENCE OF TURBULENCE MODELS AND TURBULENT SCHMIDT NUMBER FOR AN ISOLATED BUILDING : Study on prediction accuracy of CFD applied to dispersion around buildings part 1

The prediction accuracy of the flow and dispersion around a cubic building with a flush stack located on the roof were examined using various k-ε models. Numerical results were compared with the wind tunnel data. The standard k-ε model provides inadequate results for concentration field, because the basic flow structure such as the reverse flow on the roof can not be reproduced with this model. However, the revised k-ε models considered provide concentrations in better agreement with the experimental data. It is also confirmed that the prediction accuracy of the velocity field strongly affects that of the concentration field. The general agreement with the experiment in the RNG case was the best among the turbulence models tested. For computations with various turbulent Schmidt numbers, Sc_t, the results using Sc_t=0.3 gave better agreement with the wind tunnel data than those using Sc_t=0.7 and 1.0. It was confirmed that the predicted concentrations by all CFD models were less diffusive than those of the experiment and the results were largely dependent on the value of turbulent Schmidt number