Validation of CFD Simulations for Natural Ventilation

Natural ventilation, which may provide occupants with good indoor air quality and a high level of thermal comfort, and reduce energy costs, has become an important sustainable strategy in building designs. This investigation used three computational fluid dynamics (CFD) models: steady Reynolds averaged Navier-Stokes equation (RANS) modelling, unsteady RANS modelling, and large eddy simulation (LES) to study both wind-driven and buoyancy-driven natural ventilation. The validation of the CFD models used the experimental data of wind-driven natural ventilation, obtained from a wind tunnel with a scaled building model, and the data of buoyancy-driven ventilation, obtained from a full-scale chamber. LES results seem to be more accurate and informative than those obtained with the RANS modelling, but with severe penalty in computing time. This investigation has also analysed turbulence energy spectra of natural ventilation. The peak turbulence energy for wind-driven natural ventilation is at frequencies higher than that for buoyancy driven natural ventilation. Thus, the fluctuating flow field plays a more important role in determining ventilation rate for wind-driven natural ventilation than for buoyancy-driven natural ventilation.