Effect of street geometrical layout on dispersion emissions of traffic exhaust: experimental simulation

Abstract

Pollutants dispersion emitted from road traffic is a dominant source of urban air pollution. Therefore, it is necessary to quantify emission levels in urban street canyon to evaluate their impacts on the public health and the environment. In this article, we study the effect of different street geometrical layouts on dispersion emissions of traffic exhausts for winds perpendicular to the roadway. A wind tunnel experiment modeling three different street geometrical layouts was executed to examine the flow fields and the concentration distributions in urban canyon. The flow and pollutants concentration were measured using a hotwire anemometer with a split-fiber probe and a fast flame ionization detector under neutral atmospheric conditions. Flow and Dispersion characteristics were studied that included mean velocity, turbulence intensity, Reynolds stress, turbulent kinetic energy (TKE), mean concentrations, and fluctuation intensity of concentration in the street canyon. The results show that the vertical velocity and turbulent energy increases as the aspect ratio increases. The pollutant concentration increases as the aspect ratio decreases. The concentration fluctuation intensities of the aspect ratio W/H = 1 was found lower than that of the aspect ratios W/H = and . The pollutant concentration at the leeward side of the aspect ratios W/H = and 1 was higher than that in the aspect ratios W/H = . The pollutant concentration distributions measured in the experiment indicates that the variability of the street geometrical layouts in urban environment are important parameters for estimating air quality in the urban canyon.

Association between Wind Environment and Spatial Characteristics of High-Rise Residential Buildings in Cold Regions through Field Measurements in Xi’an

“…In the academic community, research on urban microclimates and spatial forms in the Western world gradually started in the 1980s and the importance of improving urban spatial forms on urban microclimates has become increasingly recognized. Currently, optimizing urban spatial forms in urban planning and architectural design has become a hot topic of research [5][6][7]. Scientifically planning the form of architectural spaces in cities is crucial in creating a favorable wind environment.…”

Influence of quadrat characteristics on the evolution of the dispersion effect for fiber–water dispersions

“…16 Therefore, determining how to control and form a uniform fiber network structure to optimize the desirable properties is significant for materials because the fiber dispersion effect is directly related to the final properties of the materials. [17][18][19][20] Particularly in a fiber-water dispersion, fibers are affected by the continuous turbulent kinetic energy from the stirred fluid, 21 and thereby form fiber webs. In particular, the presence of different fibers endows functional properties to the fiber materials.…”