Large-eddy simulations on pollutant reduction effects of road-center hedge and solid barriers in an idealized street canyon

This study conducted large-eddy simulations (LES) on the pollutant reduction effects of hedge and solid barriers in a three-dimensional idealized street canyon with an aspect ratio 0.5. The wind direction was perpendicular oblique (45°) to street. results were validated data from tunnel experiments. LES accurately predicted concentration distribution barrier-free case reproduced well barrier-induced reduction. In case, large recirculation vortex observed. However, central forced recirculated airflow middle newly formed vortices near leeward walls. two counter-direction barrier cases transported pollutants toward center enhanced vertical removal at top canyon. (solid barrier) reduced spatially-averaged by about 59% (45%) wall, 64% (20%) windward 45% (17%) whole compared case. leaf area density (LAD) width further investigated under direction. Increasing LAD or decreased walls but increased canyon-averaged concentration. direction, 30% 60% building