A new passive noise suppression technology utilizing the interactions of the airframe with the jet plume is developed here. In this technology, the flat surface of the airframe adjacent to the jet plume is modified to create a slightly wavy surface instead. Such design modification can be applied to the existing design concepts with engine mounted under the wing, as well as, to the top-mounted engine configurations. The basic principle is to design a wavy pattern to reflect the incoming near-field flow and acoustic perturbations into waves of a particular dominant frequency. The reflected waves will then excite the corresponding frequency of the large-scale structure in the initial region of the jet's shear layer. By designing the frequency of the reflected waves to be the harmonic of the fundamental frequency that corresponds to the radiated peak noise, the two frequency-modes interact nonlinearly. With the appropriate phase difference, the harmonic dampens the fundamental as it extracts energy from it to amplify. The outcome is a reduction in the peak noise. To evaluate this concept, we conducted Detached- Eddy Simulations for a rectangular supersonic jet with the wavy shield and verified our numerical results with experimental data for a jet with an adjacent flat surface. Results show that the proposed wavy surface reduces the jet noise as compared to that of the corresponding flat surface by as much as 4 dB.
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