Narrow Street Canyons Research Articles

An intra-urban thermal breeze in Göteborg, Sweden

¶The existence and character of an intra-urban thermal breeze (IUTB) in the city centre of Goteborg, Sweden was examined. The study was carried out in a 10 ha open area covered with gravel, asphalt and grass, surrounded by narrow street canyons. Measurements included an array of fixed wind and temperature sensors and smoke in the open area; temperature of the surrounding neighbourhood from mobile thermal mapping and fixed temperature sensors; standard climate measurements from four automatic weather stations in and around Goteborg.

The propagation of sound in narrow street canyons.

This paper addresses an important problem of predicting sound propagation in narrow street canyons with width less than 10 m, which are commonly found in a built-up urban district. Major noise sources are, for example, air conditioners installed on building facades and powered mechanical equipment for repair and construction work. Interference effects due to multiple reflections from building facades and ground surfaces are important contributions in these complex environments. Although the studies of sound transmission in urban areas can be traced back to as early as the 1960s, the resulting mathematical and numerical models are still unable to predict sound fields accurately in city streets. This is understandable because sound propagation in city streets involves many intriguing phenomena such as reflections and scattering at the building facades, diffusion effects due to recessions and protrusions of building surfaces, geometric spreading, and atmospheric absorption. This paper describes the development of a numerical model for the prediction of sound fields in city streets. To simplify the problem, a typical city street is represented by two parallel reflecting walls and a flat impedance ground. The numerical model is based on a simple ray theory that takes account of multiple reflections from the building facades. The sound fields due to the point source and its images are summed coherently such that mutual interference effects between contributing rays can be included in the analysis. Indoor experiments are conducted in an anechoic chamber. Experimental data are compared with theoretical predictions to establish the validity and usefulness of this simple model. Outdoor experimental measurements have also been conducted to further validate the model.

Dispersion of vehicular emission in street canyons, Guangzhou City, South China (P.R.C.)

The concentrationof vehicular pollutants, wind, turbulence and traffic volume were measured in three different typical street canyons in Guangzhou City. Air dispersion in different types of urban canyons was compared. The configuration of a street is an important factor that influences air dispersion. In low wind conditions, it is rare that a stable vortex is formed in a canyon with irregular configuration. The movement of vehicles may dominate the flow near the surface of the narrow street canyon when tee wind at roof-level is weak. Simple operational models have been proposed. They performed well in predicting the air pollution due to vehicular emission in different street canyons in Guangzhou City.

Studies of Urban Climates and Air Pollution in Switzerland

Abstract In addition to an assessment of the factors that are responsible for urban climate change, this paper describes climatological studies and peculiarities of some Swiss cities. Although these cities are small, urban air pollution presents a real problem for urban planning. This is a result of the narrow street canyons, the high traffic concentration and the complex topography, which favors air stagnation during anticyclonic weather conditions. In recent studies of urban climate and air pollution, scientists have tried to find a balance not only between modeling and observational studies, but also between specialized investigations and integrating studies which lead to an application in land-use planning and politics. In almost every city, research efforts have concentrated on the dynamics of temperature stratification and airflow. Because of the smaller size of Swiss urban areas and the existence of a complex topography, the interactions between three effects important for transport and dispersion ...