AN EVALUATION OF TWO ADVANCED TURBULENCE MODELS FOR SIMULATING THE FLOW AND DISPERSION AROUND BUILDINGS

摘要

We have presented a validation for our model through simulating the flow and dispersion around a cubical building. It was found that the LES model yields more accurate results but with roughly an order of magnitude increase in computational cost. Several conclusions can be drawn from this study: 1. Instantaneous snapshots of concentration from the LES model have similar vertical depth and width as the RANS. This indicates RANS is producing a reasonable plume, but without the spatial fluctuation associated with vortex shedding in the experimentally observed wake. 2. The RANS and LES yield similar mean velocity fields near the building. If mean velocity fields are sufficient and decoupled from the advected species, the RANS solution is the more economical method. 3. The LES can capture turbulent variations that the RANS does not model. For situations in which the source lasts sufficiently long, LES simulates more accurately the width of the dispersion than RANS does. This is useful for situations where accurate species concentrations in both space and time are important.