| Description |
Urban microclimate has an important impact on the alterations of the local climate in urban and suburban areas. These changes significantly affect pollutant transport, air quality, water and energy consumption, and the general health and comfort of urban residents. Despite extensive research on the computational modeling of urban flows, the integrated impacts of microclimate driving forces (i.e., momentum fluxes, radiative, and turbulent heat fluxes) and major urban infrastructure elements (i.e., buildings' geometrical parameters) have rarely been investigated for complex urban configurations at street-level, neighborhood, and city scales. In this study we used various computational fluid dynamics (CFD) approaches to improve the understanding of momentum and scalar (e.g., particle, energy, and moisture) transport at different time-space scales in street canyons and city districts. We investigated the role of urban layout configurations on flow regimes and transitions, flow patterns, and dominant topological features in street canyons with uneven and single-height buildings. We rigorously analyzed the performance of the CFD methods on predicting and tracking the dynamics of major flow topological features in different flow regimes. At a broader scale, we studied the spatiotemporal characteristics of mean and turbulent momentum and scalar transport and their correlations with the morphological parameters in city districts. Finally, we introduced a high-performance fast-response environmental simulation software for dynamic modeling of mass, momentum and energy exchange processes at city districts during diurnal cycles. We studied the validity of the software for a complex urban area during a full day of field experiment at the University of Utah campus. Our findings showed that urban layout configurations strongly influenced the existence, transition, and spatial variations of the flow features including vortex pairs, secondary vortices, rooftop recirculation zones, saddle points, in-canyon separation points, and wake fields. At broader scales, the urban morphology and surface characteristics altered the spatially-averaged turbulent flow features, particle concentration, and energy transport in city districts and complex urban areas. Overall the results of this study provided beneficial information and computational tools for decision-making studies in urban design, city planning, and building energy analysis. |
