NUMERICAL AND EXPERIMENTAL MODELING OF THE 3-DIMENSIONAL TURBULENT WIND FLOW-THROUGH AN URBAN SQUARE

Urban design and planning may require detailed data on the wind flow around buildings, within the streets and through the squares to ensure the safety and the comfort of pedestrian. Our aim was to compare a numerical prediction of wind flow through a complex and realistic building site with an analogic test in a boundary layer wind tunnel. The chosen site was a semi-circular square located in downtown Nantes, France. Five streets lead to the square which is made up of four buildings with double sloping roofs and a church with a dome. The wind flow within the streets and through the square was calculated using a standard k-epsilon model of turbulence. The spatial finite elements discretization consisted of about 60, 000 nodes. The results of the numerical simulation were compared with wind tunnel measurements made in the CSTB large facilities. The wind velocities were in fairly good agreement. Nevertheless, the complete experimental velocity field was not measured, especially in the wakes behind the buildings or in the recirculating zones on the square, because of the limits of the triple hot wire probe used. Therefore, the use of an other measuring technique, laser anemometry, is now being considered.