The update process and characterization of the são paulo university wind-tunnel for aeroacoustics testing

The aircraft noise is one of the major environmental problems of the population living around big airports. In order to study this many aeroacustic test facilities have been constructed or adapted around world. The present paper shows the results of the update of a previous aerodynamics wind-tunnel into a wind-tunnel with capacity to execute aeroacoustics tests, while keeping its good aerodynamic qualities. In order to reduce the wind tunnel background noise level, melamine foam was applied on wind-tunnel walls, and an acoustic baffle was installed between corner vane sections. Also a treatment was applied to the tip fan to the tip fan blades and the noise generated by the electric motor was insulated. Results showed a reduction of up to 5 dB and a noticeable removal of spectral tones after the wind-tunnel treatment. Another positive effect of the noise reduction was the decrease of test section turbulence, from its previous level of 0.25% to 0.21%. As a minor penalty, the insertion of noise treatment caused a maximum flow velocity maximum reduction of 2% for the same electric power input. All this process, described by the present paper, resulted on a wind-tunnel with good flow quality and capacity for aeroacoustics measurements.