Atmospheric wind tunnel

This open-circuit atmospheric wind tunnel has a 26-metre long test section and a cross-section of 2 m x 2 m, with transparent walls and floor and ceiling adjustable in height. Its centrifugal fan powered by a 45kW motor allows for maximum wind speed of 10 m/s.

It is therefore a remarkable piece of equipment to investigate atmospheric boundary layers and their interaction with vegetation or urban canopies at 1/200 scale.

Besides measurement of reference flow parameters (i.e reference wind speed, flow temperature, hygrometry, atmospheric pressure), different types of measurement method can be employed in this wind tunnel:

• 32-channel acquisition system equipped with 24 thermal anemometers dedicated to the use of single or multiple hot-wire probes,
• stereoscopic Particle Image Velocimetry (SPIV) system composed of a 200mJ Nd-YAG pulsed laser, two 4M pixels cameras with their dedicated synchronization, acquisition and post-processing unit,
• drag balance designed for the measurement of canopy element drag (< 0.5N),
• unsteady wall-pressure transducers (8 channels) and mean pressure transducers (96 channels).

The SPIV system quasi-systematically employed in this wind tunnel provides measurements of the three-component velocity in a plane (typically more than 16 000 instantaneous velocity vectors), therefore allowing for the detailed investigation of turbulent flows within and above dense canopies.

Fully operational since 2009, this wind tunnel has been used in the following research projects :

• EM2PAU (2008-2012): flow within street canyons
• VEGDUD (2010-2014): dynamical interaction between vegetation canopies and the lower atmosphere and vegetation-urban terrain transition
• TIPEE (2013-2016): evaluation of the pressure coefficient on a building in a restored neighborhood
• URBANTURB (2015-2018): dynamical coupling between the urban canopy and the atmospheric surface layer