Two atmospheric boundary layer wind tunnels are used for wind engineering studies of building behavior, modelling urban wind conditions at reduced scales. They accurately reproduce the static (velocity gradient) and dynamic (turbulence) characteristics of wind on site and the environment around the tested structure.
The NSA wind tunnel
The NSA wind tunnel is a speed- and temperature-controlled closed-circuit wind tunnel. Its main test section measures 20 meters long, 4 meters wide, and has an adjustable height ceiling of 2 to 3 meters. The simulation scales are between 1:100 and 1:500 but may be up to 1:5000 for terrain studies. The flow speed in the test section is variable from 0 to 30 m/s, controllable to +-0.1 m/s. The NSA wind tunnel is particularly well suited for sizing such as wind force measurement, pressure fields, and the dynamic behavior of large structures. It can also be used to conduct comfort and pollutant dispersion studies.
The NASA wind tunnel
The dimensions of the NASA wind tunnel are comparable to those of the NSA wind tunnel. Its speed is variable from 0 to 9 m/s. It is used in particular for studies requiring lower flow velocities, such as stability studies for tower cranes. Its porous walls permit work at scales of the order of 1:100 undisturbed by blockage effects.