Aeroacoustic performance of multi-stream, rectangular, supersonic jets

Multi-stream, variable cycle point, turbofan engines with rectangular exhaust profiles are in consideration for future tactical aircraft. Such engine architectures aim to combine the benefits of low-profile, simple geometry nozzles with the ability to cycle between high-thrust and high-efficiency operation as required by the demands of the flight profile. There exists a need to improve the understanding of the aeroacoustic characteristics of low bypass ratio, multi-stream rectangular exhaust jets. This work reports on a series of experiments that have been performed in an effort to begin meeting this demand. Model-scale far field acoustic data are reported for heat-simulated, supersonic, dual stream, rectangular jets. Acoustic data are compared with far field noise measurements of single round and rectangular jets operating at equivalent thrust and mass flow rate jet conditions. Dual stream jets demonstrate the potential for noise reductions over 4 dB OASPL in the peak noise emission direction compared to single stream equivalent jets.