The relative importance of anthropogenic heat and wall heat flux on the street canyons warming: A multi-physics numerical simulation

Street canyon warming is influenced by both solar-heated walls and anthropogenic heat releasing. This study aims to evaluate the relative importance of anthropogenic heat emissions and wall heat fluxes induced by realistic solar heating on the air temperature in 2D street canyons. Computational fluid dynamics (CFD) simulations were conducted, considering two anthropogenic heat emitting locations (from side-wall or roof-top), three building-height arrangements (uniform-height, varied-height, elevated buildings), two aspect ratios (H/W = 1 or 3) and two wall heating patterns: leeward-wall heating (L-H, representing 9 a.m.), all-wall heating (A-H, representing 7 p.m.).

The results indicate that anthropogenic heat emissions from side-wall exert a greater warming effect, significantly influencing both pollutants and airflow field. The air temperature in H/W = 3 is higher and thermal buoyancy is more prominent. Heat emitted from side-wall elevates average air temperatures inside street canyon by 2.3 K (L-H), 2.1 K (A-H) compared to scenarios without additional heat release, and 1.6 K (L-H), 1 K (A-H) when emitted from roof-top. Varied-height buildings are characterized by the highest air temperatures (up to 3.7 K warming in H/W = 3) and pollutant concentrations due to poor ventilation. Elevated buildings enhance turbulent ventilation and reduce the warming effects of anthropogenic heat and solar radiation in deep street canyons.