Air flow around isolated gable-roof buildings with different roof pitches: Wind tunnel experiments and CFD simulations

Abstract

The air flow around isolated gable-roof buildings with different roof pitches was investigated by wind tunnel experiments and computational fluid dynamics (CFD) simulations based on a steady Reynolds-averaged Navier–Stokes equations (RANS) model. Firstly, wind tunnel experiments on the air flow around building models with three different pitches, specifically, 3:10, 5:10, and 7.5:10, were conducted to create a measurement database of the time-averaged velocity, turbulent kinetic energy, and pressure coefficient around the building. Next, sensitivity analyses for the grid resolutions and turbulence models of the CFD simulations were performed for the 5:10 roof pitch model. The performance of the CFD simulation with the selected grid resolution and turbulence model was examined and validated by comparing the results of the simulation with the measured data for all the roof pitches. Generally, for the streamwise velocity, the simulation results were found to be in good agreement with the measured values, with an average deviation of less than 15%. For points behind the building, however, the prediction accuracy showed as much as 30% deviation. This discrepancy was closely related to the fact that the transient fluctuations caused by vortex shedding around the building are not reproduced by the steady-RANS simulations used in this study. Finally, the effect of the roof pitch on the flow field around the building was investigated using the CFD simulations. We clarified that the difference in the flow fields of the 3:10 and 5:10 roof pitches is large, relative to the difference between the 5:10 and 7.5:10 pitches.