Influence of Different Configurations of Microjet Injection on Structure and Acoustic Radiation of Supersonic Jet

The work is devoted to experimental study of the structure and acoustic radiation of a supersonic underexpanded jet Ma = 1, Npr = 5 with the presence of vortexgenerators in the form of small-sized jets injections. Ten different configurations were tested, in which following the gas-dynamic and geometrical parameters of the microjets were changed one by one: microjets pressure, the injection distance from the main nozzle section, azimuthal, tangential, and axial angles of micronozzles inclination. The flow visualization, azimuthal Pitot pressure profiles and characteristics of jet noise in the far field were obtained. It has been revealed that the injection of microjets in general leads to an increase in the jet long-range and a decrease in its mixing. The advantageous parameters of the microjets injection for reducing the jet acoustic emission are the injection point vicinity to the main nozzle section, micronozzles inclination to main jet axis and the small tangential angle of micronozzles. The micronozzles quantity effect is non-linearly in relation to the structure and the jet noise. The average pressure measuring distribution near artificial longitudinal vortices in a jet stream cannot predict the characteristics of its mixing and acoustic radiation.

Download Full-text

Energy transfer mechanism of supersonic jet noise through rectangular nozzles

Noise Control Engineering Journal ◽

10.3397/1/376431 ◽

2017 ◽

Vol 65 (2) ◽

pp. 110-120 ◽

Cited By ~ 1

Author(s):

Zhe Chen ◽

Jiu-Hui Wu ◽

A-Dan Ren ◽

Xin Chen ◽

Zhen Huang

Keyword(s):

Energy Transfer ◽

Supersonic Jet ◽

Jet Noise ◽

Transfer Mechanism ◽

Energy Transfer Mechanism ◽

Supersonic Jet Noise

Download Full-text

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.

Download Full-text