Experimental and numerical study of fluidic corrugation design for supersonic jet noise reduction

The results of this paper summarize an extensive parametric experimental and computational study performed to improve understanding of the on-demand fluidic corrugation noise reduction technology pioneered at Penn State University. This noise reduction technique creates fluidic corrugations via actively-controlled, precise blowing in the divergent section of a converging-diverging nozzle. Researchers at Penn State recognize that a crucial intermediate step in implementing this technology on full-scale aircraft is its extension to industry laboratory scale. This study forms the technology basis for industry-scale experiments going on in parallel to those at Penn State. The injectors producing each corrugation are defined by 4 physical parameters: injection angle, diameter, streamwise position in nozzle, and operating pressure. Each corrugation is additionally defined by the number of injectors generating the corrugation. By altering each of these parameters individually greater insight is gained on optimal fluidic corrugation design for supersonic jet noise reduction. Initial experiments with 3 injectors/fluidic corrugation showed OASPL reductions comparable to prior experiments using 2 injectors/corrugation. In contrast to 2 injectors/corrugation studies, 3 injectors/corrugation experiments showed greatest noise reduction with the downstream injector operating at lower pressures. RANS simulations provided evidence that the middle injector further decreases the momentum of the core nozzle flow allowing the downstream injector to penetrate farther into the core flow at lower operating pressures. Peak mixing noise was reduced by nearly 4dB OASPL using fluidic corrugations generated by 3 injectors.