JARF

The Jet Aeroacoustics Research Facility at the Experimental Aerodynamics Division at NAL enables comprehensive investigation of jet aeroacoustics with its capability for both flow and acoustic measurements. The Jet Aeroacoustics Research Facility (JARF) is an advanced aeroacoustics test bed to facilitate both existing and future national programs and basic research projects on jet-noise. The facility consists of an anechoic chamber of dimensions 4.2m (L) x 3.6m (B) x 3.6m (H) with a low- frequency cutoff of 330 Hz. The anechoic chamber has removable floor wedges and a treated catcher and duct to minimize external influences. The function of the anechoic chamber is to eliminate or minimize (within specified tolerances) the reflected or scattered sound energy from a source. If the reflected energy is small such that freefield conditions are approximated, the SPL from a point source emanating spherical waves should decrease in proportion to the radius squared (or 6 dB per distance doubling). The chamber has been calibrated from 250 Hz to 4000Hz along eight directions using an omni-source. The deviation from the Inverse Squared Law at 500Hz is well within the permitted 1.5dB.

The facility incorporates a PID-controlled jet rig to provide supersonic (up to Mach 2.0) and subsonic jet flows with nozzle diameters up to 50mm. The jet rig is equipped with a low noise fisher valve and a settling chamber specially designed to minimize rig noise. An inline heater provides capability to generate heated jets with an exit temperature of 600K.

The facility is equipped with a polar microphone array and a data acquisition system capable of simultaneous data acquisition. The experimental capabilities of this facility include flow measurements via Particle Image Velocimetry (PIV) and Background Oriented Schlieren (BOS) as part of the effort to link flow-field and noise-field

measurements. This facilitates the study of fundamental aeroacoustic problems such as mixing noise as well as focused applications such as acoustic loading at lift-off.

Calibration of JARF