Scaled outdoor validation of the water body model and numerical studies on their impact on urban blocks

Water bodies, whether natural or artificial, are prevalent features in urban landscapes. Studies have shown that they are among the effective strategies for mitigating the urban heat island (UHI) effect. However, research on the interaction between water bodies and buildings, particularly those incorporating the impact of solar radiation and evaporation, remains limited. This study validates a numerical model that accounts for solar radiation and evaporation through a scaled outdoor experiment. The experiment was conducted in Xingtai City, Hebei Province (37°17′N, 114°32′E) over 28 days in the autumn of 2024. Wind temperature, humidity, and radiation at various heights were monitored in the 2D street canyon, both with and without water coverage, with evaporation rates innovatively monitored using a weighing method. Meanwhile, CFD simulations based on this model investigate how solar incidence time and water body size influence surrounding airflows, air temperature, and thermal comfort in an idealized urban block. The numerical simulations considered five water surface areas, ranging from 0% to 900% of the central position in a 7×7 idealized building cluster, along with three solar elevation angles (0° and ±45°). The goal is to provide insights into the maintenance and design of water bodies in urban development.