Numerical Simulation of Airflow and Pollutant Dispersion Around High-Rise Buildings with Different Rotation Angles

The increase in urban building density will have a significant impact on pedestrian wind environments, especially in high-density urban building environments. Architectural designers should consider the impact of the urban microclimate through reasonable architectural designs and layouts, effectively improve the pedestrian wind environment, and enhance the comfort of urban dwellers and the sustainable development of cities. Therefore, on the basis of the Reynolds number average Navier–Stokes (RANS) method, a standard k-ε turbulence model was adopted to simulate the effects of high-rise buildings with different rotation angles on the flow and dispersion of pollutants. The results showed that the rotation angle has an obvious influence on the flow structure, turbulent kinetic energy, and near-ground concentration, and the effect is more significant with the increase in building height. When the building is rotated by a certain angle (10°, 20°, and 30°), the whole flow is deflected and no longer symmetrical. When the rotation angles are 20° and 30°, it is found that two large vortices are formed in the wake region of the entire building array, as if the building array can be regarded as a whole. Because the pollution source is located in the recirculation zone or the reverse-flow zone, the high-concentration area is mainly concentrated upwind of the source. As the building is rotated counterclockwise (10°, 20°, and 30°), the pollutant plume is also deflected counterclockwise, presenting an asymmetry.