Experimental results for supersonic jet noise reduction using nozzle fluidic inserts

This paper describes further development of an active noise reduction method using fluidic inserts. Fluidic inserts blow bypassed air into the divergent section of a convergingdiverging nozzle and are actively controlled to minimize effects on engine performance. The fluidic inserts are aligned in the nozzle to create a corrugation simulating the effect of a hard-wall corrugations. Previous studies have shown that the fluidic insert method reduces both the peak mixing noise and the broadband shock associated noise. The goal of the current research is the optimization of the fluidic insert noise reduction method through parametric studies. The present study focuses on varying the number of fluidic corrugations and their azimuthal positions. Noise measurements using four fluidic corrugations with both evenly spaced and unevenly spaced azimuthal positions are compared to previous experiments with three and six evenly space fluidic corrugations.