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 scien-tific research in recent years since complex flow patterns evolve leading many times to bad com-fort conditions for the pedestrians and the habi-tants. Within that frame, the main aim of this study is the creation of a semi-empirical algo-rithm for accurate wind speed computation in-side street canyons. A big experimental campaign took place in Athens in the summer of 2001 where measure-ments were taken in five different urban street canyons in the framework of the Urbvent Euro-pean Research project. The experimental data set includes wind speed and direction measure-ments within and above the canyon, on the roof-top 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 dif-ferent 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 com-puted wind speed values, derived from the semi-empirical model, resulted into agreement