Comparison of computed and measured wind fields within street canyons

Natural ventilation is one of the most efficient passive cooling techniques for buildings. Knowledge of the wind speed in street canyons is the necessary condition for the application of such a technique in dense urban configurations. Thus, prediction techniques to evaluate the mi-croclimate and dispersion parameters in street canyons, has become a subject of intense scien-tific research. In most cases, wind flow and pol-lutant dispersion characteristics have been stud-ied numerically and experimentally. The micro-scale model MIMO was employed in order to perform a three-dimensional modelling of the wind field within three typical deep street can-yons, located in the centre of Athens. Computa-tional results were compared to field data col-lected during consecutive three-day experimen-tal campaigns that took place in the summer pe-riod. Results from the computations have shown that the wind field in urban areas is quite com-plex, presenting areas of very low wind speeds and convergence of vortices. The model under-estimated the measured wind speed intensities, which may be partly explained by the uncer-tainty of specific input parameters, the neces-sary simplifications for the application of such models and finally the geometrical complexity of the area modelled. Finally, computations were performed for a reference velocity of 2.5 m/s, which is considered to be a threshold value. The wind field developed departed from the one observed in the previous cases. 1