The ACOUS facility is composed of a jet discharging in a semi-anechoic room (4 m x 3 m x 4 m) whose walls, ground floor and ceiling are covered with acoustic absorber. The air exhaust is acoustically insulated from outside. The cut-off frequency of the semi-anechoic room is 350 Hz.
The diameter of the nozzle outlet is 41 mm. The air is supplied to the settling chamber by ejectors connected to a 7 bar compressed air network. The actual maximum velocity at the nozzle outlet is about 75 m/s. The steel nozzle is mounted on a wooden settling chamber fitted with acoustic damping to decrease the air supply noise, and with grids to achieve a turbulence level below 0.3%. The low turbulence level, together with a high contraction ratio, allows to obtain a laminar boundary layer at the outlet of the nozzle.
The settling chamber contains a loudspeaker, used to excite the jet shear layer, and to stabilize and promote various vortex ring interactions. Microphones are placed on a directivity support, a hot wire anemometry system is installed, and an optical access in the room wall allows to carry out Particle Image Velocimetry measurements.
The facility is used for the investigation of the coherent structures that are created in the jet shear layer and of the noise generated by their interactions. The dipole-like noise source produced by an object (cylinder or airfoil) placed at various downstream distances from the jet exit is also investigated. The facility can also be operated with two coaxial subsonic axisymmetric air jets. The diameter of the second nozzle outlet is 23.5 mm and the outlet velocity of the second jet can be set independently from the first one up to about 75 m/s.