Aeroacoustic carousel

Closed-Circuit wind tunnels in which air is driven by fans are widely used for aerodynamic testing. For aeroacoustic tests, in which the radiated sound field must be measured in the presence of flow, they have two major problems: the fan makes them noisy, and the hard walls make them reverberant. The ideal aeroacoustic test facility would be quiet and anechoic. It is difficult to satisfy these requirements in a standard wind tunnel because anechoic and noise-muffling treatments tend to increase flow resistance so that the fan has to work harder resulting in more noise. In this Note a novel alternative that will eliminate the fan and allow as much anechoic treatment as desired will be proposed