How can street interface morphology effect pedestrian thermal comfort: A case study of the old town of Changsha, China

Abstract

The challenge of the urban thermal environment stands as a pivotal obstacle in enhancing urban habitation, with its most conspicuous manifestation occurring during the summer months. The urban configuration intertwines with the thermal milieu, and its meticulous refinement is critical to ameliorating thermal conditions. Notably, streets, constituting two-thirds of the urban expanse, assume paramount importance. Delving into the nexus between street interface morphology and the thermal environment carries practical implications. The current corpus of street form research exhibits a conspicuous oversight in attending to the street interface, with a noticeable need for more exploration into its symbiosis with the thermal ambience. This study, therefore, directs its focus toward the nuanced examination of street interface morphology. Employing the method of constructing morphological models, we utilize ENVI-met software to simulate and analyze the thermal environment. The Universal Thermal Climate Index (UTCI) serves as the yardstick for evaluating thermal conditions, elucidating the influence of street interface morphology on the summer thermal environment of streets. The findings unveil a discernible correlation: for east-west streets, diminished interface density and concavity, coupled with an augmented street aspect ratio and interface height dislocation, yield superior street pedestrian thermal comfort. The interface height ratio index emerges as a particularly noteworthy factor, with the nadir of thermal comfort occurring at an interface height ratio1. Moreover, streets boasting elevated interfaces on the north side exhibit enhanced thermal comfort within similar interface height ratios. In the case of north-south streets, heightened interface density and street aspect ratio, juxtaposed with diminished interface concavity and height dislocation, parallelly yield enhanced thermal comfort. Optimal thermal comfort materializes when the interface height ratio equals 1. Moreover, streets featuring elevated interfaces on the east side manifest superior thermal comfort within equivalent interface height ratios. The culminating phase of this inquiry entails the optimization simulation of select streets within the ancient precincts of Changsha. The outcomes underscore a discernible enhancement in the thermal comfort of both east-west and north-south streets post-optimization, affirming the efficacy of street interface shape transformations in efficaciously augmenting the summer thermal environment of urban streets.