Acoustic shielding benefits for jet noise of engineover-the-wing for conventional aircraft (CTOL) application were studied with and without forward velocity for various small-scale nozzles. These latter included convergent, bypass and mixer, with and without forward ejector, nozzles. A 13-inch free jet was used to provide forward velocity. Farfield noise data were obtained for subsonic jet velocities from 650 to 980 ft/sec and forward velocities from zero to 260 ft/sec. The studies showed that although shielding benefits were obtained with all nozzles, the greatest benefits were obtained with mixer nozzles. The absolute magnitude of the jet noise shielding benefits with forward velocity was similar to the variation in nozzle-only noise with forward velocity.

Utilizing a static test stand, 6-by 9-foot wind tunnel and 13-inch circular free jet, aerodynamic and acoustic data were obtained with a convergent circular nozzle, bypass nozzle, 6-tube mixer nozzle, and 6-tube mixer nozzle with an ejector. The aerodynamic data consist of velocity decay surveys with and without forward velocity. .The acoustic data include total sound power, directivity and frequency spectra obtained statically and with forward velocity. The relation of aerodynamic and acoustic measurements statically and in forward flight for the various nozzle configurations are discussed.

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The effect of nozzle roof (kickdown) angle and nozzle location relative to the wing trailing edge on noise was determined at model scale with a 5:1 slow nozzle (equivalent diameter, 5.1 cm) for several OTW configurations. Nozzle roof angles of 10° to 40°, with and without cutback at the nozzle sides were tested. Also included, for comparison, was a 5:1 slot nozzle with external deflector. Three wing chord sizes were used: standard (33 cm), 23-standard, and 32-standard. Flap deflection angles used were 20° and 60°. The nozzle was located at 20% and 35% of chord. In addition, velocity maps were obtained at the trailing edge of the wings. With increasing wing size, representing a variety of airframe/engine installations, low-frequency noise was increasingly attenuated and shielding benefits increased directly with wing size. With increasing nozzle roof angle, the jet velocity at the trailing edge was decreased, causing a decrease in trailing-edge noise; however, the jet impingement noise on the wing increased. Cutback of the nozzle sides improved flow attachment and reduced the trailing-edge velocity and noise. The best flow attachment and least trailing-edge noise was obtained with the external deflector configuration.