Canyon effects: Calculation of wind speed in an urban street canyon with the aid of a semi-empirical model based on experimental data

The microclimate and dispersion in urban street canyons has become a subject of intense scientific research in recent years since complex flow patterns evolve leading many times to bad comfort conditions for the pedestrians and the habitants. Within that frame, the main aim of this study is the creation of a semi-empirical algorithm for accurate wind speed computation inside street canyons. A big experimental campaign took place in Athens in the summer of 2001 where measurements were taken in five different urban street canyons in the framework of the Urbvent European Research project. The experimental data set includes wind speed and direction measurements within and above the canyon, on the rooftop of the buildings, as well as wind speed measurements near the building walls at several heights at 30 sec intervals. The experiment lasted three days at each canyon. The experimental data were grouped into different categories based on the wind speed and incidence angle on the canyon axis. Following that a semi-empirical model was created for each wind direction and wind speed category based on already existing algorithms. Comparison between measured and computed wind speed values, derived from the semiempirical model, resulted into agreement.