Some experimental results on wind fields in a built environment

The assessment of the response of structures to the action of strong winds is essential for safety and economic reasons. In designing structures in a built environment, account should be taken of both shield effect and amplification of wind velocity due to the presence of obstacles, as well as of the specific turbulence structure. A preliminary problem is the check of the adequacy of the simplified models of representation of the variation of the wind speed with height, and, in case of adoption of the logarithmic law, the characterization of the surface roughness by means of the aerodynamic roughness length. In this paper, the results of some tests on the influence of different arrays of buildings are presented: the tests have been carried out in the wind tunnel of CRIACIV in Prato, Italy. The roughness has been realized by gluing on a plywood baseboard wood cubes in a staggered pattern; varying the surface density of the cubes, three different roughnesses have been obtained. The influence on the roughness of the geometric aspect ratio of the obstacles has been studied.