Design of a facility for shock-cell noise investigation on a subsonic/supersonic coaxial jet

Shock-cell noise is an aeroacoustic phenomenon that occurs in aeronautic engines when the nozzle is not adapted to the atmospheric pressure. In civil aircraft at cruise the secondary flow is often supersonic, thus the onset of a shock-cells system and broadband shock-associated noise as a consequence. This paper aims to describe the design of the new facility FAST (Free jet AeroacouSTic laboratory), completed in 2015, with the aim to investigate experimentally the shock-cell noise phenomenon on a dual stream jet. The rig consists of a coaxial open jet with supersonic capability for both primary and secondary flow. A coaxial silencer is used to remove the spurious noise coming from the feeding lines. The design has been validated by the use of CFD simulations. A preliminary experimental test campaign with the single supersonic jet is presented. Fine scale PIV coupled with a microphone array in the far field have been compared with analogous research in this field.