Design and performance of the aeroacoustic wind tunnel of Politecnico di Milano

The present paper describes the design and qualification activity of the new anechoic wind tunnel built at the Aerodynamics Laboratory of the Department of Aerospace Science and Technology of Politecnico di Milano. The facility features a 4 m × 4 m × 4 m anechoic test chamber with a cut-off frequency of 150 Hz. The open-circuit wind tunnel is characterized by an open test section featuring a nozzle with a 0.7 m × 0.5 m outlet section and a collector with a 1.5 m × 1.5 m inlet section, for a maximum achievable speed of 42 m/s. The paper describes the main components employed for the design of the facility and the most relevant results obtained from the aerodynamic qualification of the jet flow and from the acoustic measurements performed in the test chamber. In particular, flow quality measurements showed a high degree of uniformity of the jet and enabled the identification of the jet’s effective section along different planes past the nozzle outlet section. Moreover, hot-wire anemometry surveys enabled the identification of the turbulence intensity of the jet, having a value around 0.14% just behind the nozzle outlet section at operating conditions. Acoustic qualification results demonstrated low background noise levels, comparable to state-of-the-art academic wind tunnels of similar scale and performance. Furthermore, acoustic measurements conducted on benchmark cases, specifically a circular cylinder and a NACA 0012 airfoil, aligned with existing literature, confirmed the facility’s suitability for aeroacoustic research in aeronautics. The facility fills a major national academic infrastructural gap, providing a strategic platform for the scientific advancement of the Italian aeroacoustics community, with testing capabilities specifically tailored to novel Advanced Air Mobility (AAM) configurations.