Development of a didactic demonstrator for flow-induced noise mechanisms and mitigation technologies.

A small didactic wind tunnel demonstrator has been designed and manufactured at the von Karman Institute for Fluid Dynamics to illustrate the physical principles at stake in flow-induced noise generation, offer an audible perception of the effectiveness of noise-mitigation strategies, and serve as a practical test bench for aeroacoustic education and research. Seven mitigation technologies are embedded in a single facility, which addresses the noise generation by an airfoil, noise propagation in a duct, and noise transmission through a flexible panel. A challenging objective of this facility was to offer a perceptible impression of various aeroacoustic noise mechanisms at low flow speeds and a live assessment of the effectiveness of noise-reduction technologies. Different approaches combining multiple microphones, advanced signal-processing techniques, and real-time audio feedback have been implemented to this end. A digital twin has been developed to assist the design of the facility and test the concepts implemented in it. The results establish that the demonstrator enables a clear perception of the effectiveness of the noise-mitigation technologies. The facility is also suitable for fast and inexpensive preliminary investigations of future noise-reduction concepts, taking advantage of rapid prototyping techniques.