Flow and acoustics of supersonic cruciform jet

The experimental article focuses on the flow characteristics and acoustic features of a jet issuing from a Convergent Divergent (C-D) nozzle with a cruciform (cross-shaped) cross-section. The design Mach number is 1.5. The cruciform nozzle has an equivalent exit diameter of 5.42 mm, and its features are compared with the equivalent circular and square nozzles. The operating Nozzle Pressure Ratio (NPR) is varied from 2 to 6. The pitot probe and microphone, in conjunction with data acquisition instruments, provide the total pressure and acoustic measurements of the jet flow. The cruciform jet exhibits a shorter supersonic core length compared to both the circular and square jets for all operating NPRs. Compared to circular and square jets, the cruciform jet has a maximum Overall Sound Pressure Level (OASPL) reduction of 7.06 dB and 7.73 dB at NPR 5. The screech is suppressed and is only discernible at NPR 5 in the cruciform jets, whereas it exists from NPR 3 to 6 in the other two jets. The higher screech amplitudes are localized to lower emission angles from 45° to 75°. Together, the OASPL, and screech are suppressed in cruciform jets.