Model based study of various configurations of jet crossing a cavity. Application to the CEPRA 19 wind tunnel of propulsion test center (CEPr)

A scale model study of a jet crossing the cavity made by the chamber of an anechoic wind tunnel was undertaken. The length of the free jet and the dimensions of the diffuser inlet were varied. Cavity resonances due to aeroacoustic coupling which can prevent measurements from being made, were investigated. Background noise was measured. The aerodynamic characteristics of the jet and the reverse flow within the cavity were studied. A collector compatible with test sections of 2 and 3 m diameter was defined for the CEPRA 19 wind tunnel. For a given collector, critical velocity increases with jet length. Long test sections with large collectors canalize reverse flow near the walls. Velocity distribution in the potential cone remains good, with stability in time. Loss of relative pressure due to the free test section increases linearly with the length of the latter.