Street Canyon Vortex & Pollutant Trapping

Real streets lined by buildings on both sides act as "urban canyons" — and the ratio of building height to street width (H/W) decides whether traffic pollution gets flushed away or trapped at head height. This simulation solves the mechanically-forced canyon vortex that forms when wind blows across the roofline, drives it from Oke's classic isolated-roughness / wake-interference / skimming-flow regime classification, and releases a continuous stream of pollutant particles from a street-level traffic line source so you can watch them get swept toward the leeward wall and stack up there — while the windward wall, fed by the vortex's fresh descending air, stays comparatively clean. Drag the aspect-ratio slider from a wide boulevard to a narrow skyscraper canyon and watch the flow regime — and the leeward:windward pollution ratio — change in real time.