Acoustic liners for jet-installation noise reduction

A Helmholtz resonator with a curved cavity is studied for reducing jet-installation noise in configuration comprised by subsonic jet and nearby flat plate. The face-sheet are designed the Guess method impedance verified through an experiment simulation of tube. Both single double degree-of-freedom liners, latter perforated septum inside cavity, studied. good agreement obtained curves from design experimental numerical tube, particularly at frequencies close to absorption peak. Numerical simulations installed performed array resonators placed plate on lower side, targeting reduction ground observer. Far-field spectra show that order 7 dB respect baseline solid plate, resonance frequency liner. Moreover, there broad range around which sound pressure levels lined lower. For resonator, further (approximately 3 dB) higher frequencies, second peak coefficient curve. results also slight (2 - occurs observer shielded side but significantly narrower band frequency. This attributed acoustic waves itself prior their scattering trailing edge, coupled less abrupt discontinuity edge. Consequently, act strength source