Fine-scale characterization of urban atmospheric turbulence for reproduction in multi-fan wind facility

The rapid development of drone activity demands that devices be tested in conditions that reflect real-world phenomena. Multi-fan wind facilities (also called windshaper) are increasingly used to test free-flying drones. Through control of individual fans, a windshaper can generate non-uniform multi-directional flows over an open jet area while actively controlling turbulence characteristics. Furthermore, previous studies have shown that multi-fan wind facilities can recreate atmospheric wind statistical properties and 3D turbulence spectra. These studies were performed at one spatial location, with all the fans operating under the same control command. Therefore, we collected three simultaneous high-frequency (10 kHz) point measurements of atmospheric flow at different spatial locations to broaden the studied capabilities from a single point to a plane.

The setup presented here consists of three synchronized three-component hotwire anemometers, which were deployed collocatedly with a sonic anemometer on an actuated rotating rack. The rack automatically aligned the hotwires with the mean flow and enabled rotation of over a 360° range. The setup was stationed on a high rooftop building in Geneva (CH) to capture the spatio-temporal characteristics of atmospheric wind and turbulence at the drone operating altitudes in an urban environment.