Analyzing the microclimatic influence of urban canyon geometry with an open-air scale model

A novel approach is developed for modeling the influence of street canyon geometry on microclimatic conditions within the urban canopy. A physical scale-model of an urban roughness array was constructed in open-air conditions to enable the measurement of climatic parameters with natural turbulence effects, potentially overcoming some of the limitations common to more conventional research techniques. Energy balance in the urban canopy is quantified using a pedestrian-centered model which allows for the computation of energy exchange between a hypothetical human body and the urban environment, based on data measured within the scale-modeled street canyons and taking into account the effects of dimensional scaling. The proposed technique is demonstrated under typical hot-arid summer conditions in a desert region, and relative pedestrian energy exchanges are compared with previous findings from full-scale measurements in a climatically-similar actual urban setting. Results show that a compact street canyon geometry may reduce pedestrian heat gain during most summer hours, if attention is paid to design aspects such as street axis orientation. The model shows the ability to reproduce patterns observed in full-scale, and to reveal distinctions which are impractical to quantify using field studies alone.