Noise Reduction in Supersonic Jets from Rectangular Convergent-Divergent Nozzles

Abstract

The design and development of noise reduction methods for rectangular supersonic, convergentdivergent nozzle jets are presented. This study focuses on the analysis of hard-wall corrugations and fluidic inserts for use in non-round rectangular nozzle jets. The baseline rectangular nozzle was tested at several operating conditions and azimuthal angles and compared to similar measurements in the literature. Hard-wall corrugations were seen to reduce the shock strength of over-expanded jets exhausting from the rectangular nozzles. This results in significant reduction of the BBSAN in the forward arc. Mixing noise reductions of over 3 dB OASPL were observed in the direction of the major axis of the rectangular hard-wall corrugation nozzle. Preliminary experiments on jets issuing from a single fluidic insert rectangular nozzle with distributed blowing were conducted. Mixing noise reductions were slightly less than for the hard-wall corrugation nozzle. For these rectangular nozzle jets, BBSAN was not significantly affected by the presence of the fluidic inserts. To exploit the fluidic insert noise reduction method for rectangular supersonic nozzle jets, a systematic parameter optimization study will be required.