Paper Excerpt | Quiet Drones Symposium | Oct 2020
Authors : Roberto Putzu , Romain Boulandet, Benjamin Rutschmann, Thierry Bujard, Guillaume Catry, Nicolas Bosson.
‘In the near future, drone usage in inhabited areas is expected to grow exponentially. The inherent noise generated is one of the concerns for this kind of vehicle.
Conventional aeroacoustic wind tunnels can be used to investigate uniform flow generated noise. Flyers are generally solidly tethered to a sting in these wind tunnels.
However, the interaction of complex environmental flows with the drone fans is expected to generate different harmonic content, especially during unsteady maneuvers. Being able to probe the aeroacoustic signature of a free-flying drone in a realistic urban and wind environment is a necessity, in particular for future certification procedures.
We have developed a new family of wind tunnels, the “WindShaper” (Noca et al. 2019 Wind and Weather Facility for Testing Free-Flying Drones, AIAA Aviation Forum), able to generate complex unsteady flows reproducing environmental gusts and shear flows.
The WindShaper consists of an array of a large number of fans (wind-pixels) that may be arranged in various patterns on demand. It is in some ways a digital wind facility that can be programmed to generate arbitrary winds of variable intensity and direction. Various weather conditions (such as rain, snow, hail, fog etc.) that reflect real world situations can be introduced. Drones are in a free-flight configuration (untethered) as in their natural state. These tests can rate drones according to their capacity in maintaining a proper flight attitude and tackling flight perturbations, especially in an urban environment.
A WindShaper was modified in order to allow aeroacoustic measurements around a free-flying drone in a turbulent flow. Particular attention was given to a design that allows the drone aeroacoustic signature to be segregated from the aeroacoustic signature of the multi-fan facility. Details on the results achieved in this new infrastructure will be presented and discussed.’
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