Noise Reduction for an Unheated Mach 0.9 Jet by Fluidic Injection

Rajput, Pankaj; Kumar, Sunil; Kalkhoran, Iraj M.

doi:10.2514/6.2017-3857

Cited by 8 publications

(7 citation statements)

References 30 publications

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“…Previous research studies have shown that momentum flux ratio ( J j / J f ) determines the resultant jet trajectory. 41,42,44 Preliminary simulations performed in this study also suggested similar behavior, 11 as low microjet injection pressures leads to low (or no) jet penetration. However, as the injection pressure is increased, substantial jet penetration is observed.…”

Section: Fluid Injectionsupporting

confidence: 70%

“…The induced streamwise vortices from the CVP enhance the turbulent mixing and thus helps to suppress the resulting mixing noise. 11 The downstream fluidic injection scheme being investigated represents a type of canonical jet in cross-flow problem, i.e. "Radial jet in annular cross-flow".…”

Section: Fluid Injectionmentioning

confidence: 99%

“…The induced streamwise vortices from the CVP enhance the turbulent mixing and thus helps to suppress the resulting mixing noise. 11…”

Section: Fluid Injectionmentioning

confidence: 99%

“…It has already been shown to be effective in enhancing mixing for supersonic 10 and subsonic jets. [11][12][13][14] In this paper, we perform a detailed parametric analysis of the DFI scheme with respect to the number of microjet injections to analyze its effect on the aerodynamic field in the vicinity of the nozzle and the resulting acoustic spectrum in the far field. In the following sections, we talk about the methodology employed for modeling the fluid flow and the aeroacoustics of the problem computationally.…”

Section: Introductionmentioning

confidence: 99%

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Use of downstream fluid injection to reduce subsonic jet noise

Rajput¹,

Kumar

2019

International Journal of Aeroacoustics

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A fluid injection scheme consisting of multiple radial microjets located downstream from the nozzle exhaust is analyzed for its ability to suppress far field jet noise. Microjets in cross flow are known to enhance turbulent mixing due to the induced stream-wise vortices. Contrary to previous studies which injected fluid either inside the nozzle or just at the nozzle exhaust, this injection scheme uses a coaxial injector tube to inject multiple equally spaced microjets perpendicular to the jet axis at an axial location downstream from the nozzle exhaust. Microjet injection closer to the jet axis leads to the formation of a counter rotating vortex pair (CVP) close to the injection location which further beaks down into stream-wise vortices as the microjet bends and follows the flow direction. Detailed Large Eddy Simulations are performed for a nozzle-injector setup operating at Mach 0.9 jet with Reynolds number %10 6 to help understand the aerodynamic and acoustic features of the interaction of this fluid injection scheme with the main jet. Permeable Ffowcs Willaims Hawkings based formulation is used for computing the far field acoustic spectra for injector setups with various numbers of injection ports (n p) at two microphone locations. It is observed that as the number of microjets is increased, it leads to reduction in the far field noise. Peak noise reduction of % 4.5 dB is observed for both locations. However, beyond n p > 4 there is a lower acoustic benefit per additional port due to spatial interference between the induced CVPs.

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Section: Fluid Injectionsupporting

confidence: 70%

Section: Fluid Injectionmentioning

confidence: 99%

“…The induced streamwise vortices from the CVP enhance the turbulent mixing and thus helps to suppress the resulting mixing noise. 11…”

Section: Fluid Injectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Use of downstream fluid injection to reduce subsonic jet noise

Rajput¹,

Kumar

2019

International Journal of Aeroacoustics

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“…В исследованиях [21][22][23] проведено моделирование вдува микроструй в расширяющейся части сверхзвукового и дозвукового сопел. Установлено, что эффективнее располагать микросопла последовательно вдоль сопла для снижения шума.…”

Section: Introductionunclassified

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

Gubanov

Kundasev

Trubitsyna

2019

SJPhys

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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.

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Flow field characteristics of a supersonic jet influenced by downstream microjet fluidic injection

Pourhashem

Kumar

Kalkhoran

2019

Aerospace Science and Technology

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Mixing characteristics of a supersonic jet influenced by a Downstream Microjet Fluidic Injection (DMFI) system are numerically investigated. The DMFI system is built on the observation of a previous experimental study that utilized transverse fluidic injection from four equally spaced injection ports placed on an injection tube at a distance downstream of a 1.5 Mach number nozzle. The measurements from these previous experiments demonstrated thickening and mixing enhancement of the jet shear layer as a result of fluidic injection. The current numerical study examines the underlying physics of the flow field, as well as the effectiveness of the DMFI system at smaller mass flow rate ratios compared to those utilized in the previous experiments. Results indicate good agreement with the trend observed by the experimental study, and considerable improvement in enhancement of the jet mixing is observed. The observed mixing enhancement is attributed to the presence of the microjet tube and fluidic injection and the consequent generation of streamwise vortices, as well as the natural separating bow shock due to the transverse flow injection.DMFI system is shown to enhance the early mixing, resulting in attenuation of the downstream turbulence production. Furthermore, the DMFI system is demonstrated to be an effective method of mixing enhancement for supersonic jets with a potential for reducing the jet noise radiation.

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Noise Reduction for an Unheated Mach 0.9 Jet by Fluidic Injection

Cited by 8 publications

References 30 publications

Use of downstream fluid injection to reduce subsonic jet noise

Use of downstream fluid injection to reduce subsonic jet noise

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

Flow field characteristics of a supersonic jet influenced by downstream microjet fluidic injection

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