Experimental study and simulation of rocket engine free jet noise

A proposed wavy shield for suppression of supersonic jet noise utilizing reflections

International Journal of Aeroacoustics ◽

10.1177/1475472x20978385 ◽

2021 ◽

Vol 20 (1-2) ◽

pp. 4-34

Author(s):

Reda R Mankbadi ◽

Saman Salehian

Keyword(s):

Large Scale ◽

Flat Surface ◽

Near Field ◽

Supersonic Jet ◽

Jet Noise ◽

Dominant Frequency ◽

Wavy Surface ◽

Initial Region ◽

Reflected Waves ◽

Free Jet

In this work we propose replacing the conventional flat-surface airframe that shields the engine by a wavy surface. 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 and without the wavy shield and verified our numerical results with experimental data for a free jet, as well as, 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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Experimental Study of the Effects of Jet Noise on an Aircraft Structure

Journal of the Royal Aeronautical Society ◽

10.1017/s0368393100130846 ◽

1957 ◽

Vol 61 (554) ◽

pp. 112-114

Author(s):

K. W. Hetzel

Keyword(s):

Experimental Study ◽

Jet Noise ◽

Aircraft Structure ◽

Noise Effects ◽

Noise Damage

Reports of noise effects on the rear fuselage structure of large British aircraft indicated that one might expect noise damage in this region on the Vickers Supermarine Type 544 aircraft. It will be seen from Fig. 1 that the jet efflux from each engine passes close to the fuselage side and under the tailplane. The fuselage structure proper is, however, protected from the heat and noise effects at the jet efflux by a fairing which is insulated at all attachments. This fairing, by virtue of its shape, is called the “ pen nib. ”

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