The significant impacts of urban canyon configuration on non-isothermal flow, ventilation, and heat removal: Insights from PIV-LIF measurements

Urban climate investigations often demand a comprehensive grasp of airflow dynamics within urban settings, notably in the context of street canyons. Despite the well-recognised disparities between two-dimensional (2D) street canyon and three-dimensional (3D) building arrays, only a limited studies have undertaken a thorough quantification of these variances across diverse domains, encompassing aspects such as ventilation, pollutant dispersion, and heat flux. In this study, we deploy a simultaneous Particle Image Velocimetry and Laser-Induced Fluorescence (PIV-LIF) technique to amass intricate flow and temperature data concerning isothermal and non-isothermal flows within both 2D street canyon and 3D building array models. Evident differences in flow characteristics and temperature distributions within and above the canyons have been observed. Notably, under non-isothermal conditions with a Richardson number of 1.12, the vertical ventilation rate and heat removal capacity along the centreline of a 2D street canyon have been determined to exceed those of 3D configuration by factors of up to 3 and 2.5 times, respectively.