Abstract
Wing acoustic-shielding benefits for CTOL application were studied for a variety of exhaust nozzles, including convergent circular, bypass, six-tube mixer, and the mixer with ejector. The equivalent diameters for the nozzles ranged from 1.6 to 2.9 in. while the wind chord was 13 in. A 13-in.-diameter free jet was used to provide forward velocity. Farfield noise data were obtained at subsonic jet pressure ratios from 1.3 to 1.7 and forward velocities up to 260 ft/sec. The data are presented in terms of SPL and PWL spectra, directivity, and total power. The studies showed that jet noise shielding benefits were attained at a directivity angle of 90° with all nozzle-wing configurations. Forward velocity, except for local regions that were a factor of nozzle geometry, did not alter the shielding benefits obtained statically; the absolute magnitude of noise shielding varied in a manner similar to that for nozzle-only operation. The shielding effectiveness (configuration SPL minus nozzle-only SPL) are discussed and compared for the nozzle-wing configurations tested. In terms of sound power spectra, the presence of the wing had only a second-order effect on noise generation.
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