scholarly journals Mach-number scaling of individual azimuthal modes of subsonic co-flowing jets

2016 ◽  
Vol 793 ◽  
pp. 209-228 ◽  
Author(s):  
R. D. Sandberg ◽  
B. J. Tester
Keyword(s):  
Mach Number ◽  
Phased Array ◽  
Internal Noise ◽  
Jet Noise ◽  
Turbulent Jets ◽  
Noise Component ◽  
Axisymmetric Mode ◽  
Jet Mixing ◽  
Mixing Noise ◽  
The Individual

The Mach-number scaling of the individual azimuthal modes of jet mixing noise was studied for jets in flight conditions, i.e. with co-flow. The data were obtained via a series of direct numerical simulations (DNS), performed of fully turbulent jets with a target Reynolds number, based on nozzle diameter, of $Re_{jet}=8000$. The DNS included a pipe 25 diameters in length in order to ensure that the flow developed to a fully turbulent state before exiting into a laminar co-flow, and to account for all possible noise generation mechanisms. To allow for a detailed study of the jet mixing noise component of the combined pipe–jet configuration, acoustic liner boundary conditions on the inside of the pipe and a modification to the synthetic turbulent inlet boundary condition of the pipe were applied to minimize internal noise in the pipe. Despite these measures, the use of a phased-array source breakdown technique was essential in order to isolate the sources associated with jet noise mechanisms from additional noise sources that could be attributed to internal noise or unsteady flow past the nozzle lip, in particular for the axisymmetric mode. Decomposing the sound radiation from the pipe–jet configuration into its azimuthal Fourier modes, and accounting for the co-flow effects, it was found that at $90^{\circ }$ the individual azimuthal Fourier modes of far-field pressure for the jet mixing noise component exhibit the same $M^{8}$ scaling with the centreline jet Mach number as that experimentally documented for the overall noise field. Applying the phased-array source breakdown code to the DNS data at smaller angles to the jet axis, an increase of the velocity exponent of the jet noise source was found, approaching 10 at $30^{\circ }$. At this smaller angle the higher azimuthal modes again showed the same behaviour as the axisymmetric mode.

Experimental Investigation on Supersonic Jet Noise

2012 ◽  
Vol 588-589 ◽  
pp. 860-863
Author(s):  
Xiao Bo Peng ◽  
Jia Ming Li ◽  
Chun Bo Hu
Keyword(s):  
Mach Number ◽  
Sound Production ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Occurrence Frequency ◽  
Correlated Noise ◽  
Experimental Conditions ◽  
Supersonic Jet Noise ◽  
Validation Criteria ◽  
Mixing Noise

A systematic study has been undertaken to quantify the effects of jet Mach number and nozzle size on the noise radiated by supersonic jets. All the tests were carried out at an experimental bench of the supersonic jet. Results indicate that the field distribution of supersonic jet screech tones is characterized with very strong directivity. Under the textual experimental conditions, if the jet Mach number remain unchanged, the diameter of nozzle throat increases gradually from 5mm to 8mm or 10mm, and the amplitude values of both the turbulent mixing noise and broadband shockwave correlated noise increase by 2-5dB, and the amplitude value change of the whistler type noise is not obvious, and the occurrence frequency of the whistler type noise decreases by more than 2000Hz; if the jet Mach number increases to 3.0 from 2.0, the amplitude value of the whistler type noise increases by more than 2dB, and the occurrence frequency of the whistler type noise decreases obviously. The experimental measurements of supersonic jet noise provide the sound production mechanism research on the supersonic jet noise with data supports and references and provide the numerical modeling of the supersonic jet noise with validation criteria.

Comparison of jet mixing noise predictions with data at high subsonic Mach number

1999 ◽  
Author(s):  
J. Wat ◽  
K. Yamamoto ◽  
R. Golub ◽  
D. Garber
Keyword(s):  
Mach Number ◽  
Jet Mixing ◽  
Mixing Noise

The Effect of Chevrons on Crackle: Engine and Scale Model Results

2011 ◽  
Author(s):  
Steve Martens ◽  
John T. Spyropoulos ◽  
Zac Nagel
Keyword(s):  
High Performance ◽  
Jet Noise ◽  
Scale Model ◽  
Small Scale ◽  
Mixing Enhancement ◽  
Noise Component ◽  
Acoustic Environment ◽  
Jet Mixing ◽  
Near Term ◽  
The Impact

GE and the USN continue to work together to find and develop practical techniques to reduce jet noise on tactical aircraft such as the F/A-18 E/F/G. Noise is an important issue for the Navy because of the harsh acoustic environment induced during operations of these aircraft on aircraft carriers and the impact to communities around Naval Air Bases and training sites. The noise generated by these systems is predominantly the noise generated by the exhaust plume due to the low bypass ratio of the engine and very high exhaust jet velocities. The main components of this jet noise are the jet mixing, shock and crackle noise. The present paper reports on progress, following Reference [1] with the F/A-18 E/F/G jet noise reduction program, which is currently focused on the USN near term goal of up to 3 dB reduction in the peak directivity direction. This goal also includes the reduction of the shock and crackle noise components. These goals are currently being pursued with nozzle plume mixing enhancement employing mechanical chevrons. These chevrons can be incorporated in the production version as a redesign of the F414 nozzle seals and do not involve the introduction of additional parts to the nozzle. This paper focuses on the effect of chevrons on the crackle noise component both in full scale on the F404 engine, and in small scale on the F414 engine nozzle in the twin configuration. The paper aims to make the case that this effect, which was first observed during ground engine testing of prototype chevrons, is a beneficial one in reducing/eliminating crackle which continues to be prevalent in high performance tactical aircraft engines today.

Hot-Jet Noise Test of a Revised Notched Nozzle

2012 ◽  
Author(s):  
Tatsuya Ishii ◽  
Nozomi Tanaka ◽  
Hideshi Oinuma ◽  
Tsutomu Oishi
Keyword(s):  
Noise Reduction ◽  
Flow Rate ◽  
High Speed ◽  
Large Scale ◽  
Jet Noise ◽  
Outdoor Environment ◽  
Engine Test ◽  
Noise Component ◽  
Jet Mixing ◽  
Noise Test

Jet noise remains a significant noise component in modern commercial aero-engines. A high-speed flow mixing with the surrounding air constitutes noise sources behind the nozzle. One noise-reduction technology is a mixing device attached to the nozzle. Several fixed-geometry mixers such as chevrons have been studied by both computational and experimental approaches. The authors have previously proposed a notched nozzle with dents allocated along the nozzle lip and discussed its ability to reduce the noise level. The revised notch was expected to suppress the broadband jet-mixing noise as well as additional noise at higher frequencies. However, further assessments are required before proceeding to a large-scale engine test in an outdoor environment. First, the influence of the gas temperature on acoustic results must be tested because the temperature affects the mean jet velocity and sound propagation. As the preliminary noise test in the previous paper was limited to the cold-jet condition, far-field noise data under the hot-jet condition should be investigated. Second, the aerodynamic performance must be evaluated. Data on the flow rate and thrust would help in considering the aerodynamic performances between the baseline, notched, and chevron nozzles. This study focuses on noise tests for the finer-notched nozzle under the hot-gas condition. A small jet engine for model jet planes was employed to generate a high-temperature jet. An engine test stand was designed to monitor the engine performance data, consisting of the pressure and temperature at several positions, the fuel flow rate, and the thrust. The hot-jet test with and without the mixing device served as a compact and flexible test for aerodynamic evaluation of the nozzle. The noise test results under the hot-jet condition with this rig showed that the noise reduction characteristics of the finer-notched nozzle are different from those of conventional mixers.

Effects of forward flight on jet mixing noise from fine-scale turbulence

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 1261-1269 ◽  
Author(s):  
Christopher K. W. Tam ◽  
Nikolai Pastouchenko ◽  
Laurent Auriault
Keyword(s):  
Fine Scale ◽  
Forward Flight ◽  
Jet Mixing ◽  
Mixing Noise ◽  
Scale Turbulence

The effects of forward flight on jet mixing noise from fine scale turbulence

2000 ◽  
Author(s):  
Christopher Tam ◽  
Nikolai Pastouchenko ◽  
Laurent Auriault
Keyword(s):  
Fine Scale ◽  
Forward Flight ◽  
Jet Mixing ◽  
Mixing Noise ◽  
Scale Turbulence

Prediction of jet mixing noise at high subsonic flight

1997 ◽  
Author(s):  
Kingo Yamamoto ◽  
Joseph Wat ◽  
Thomas Austin ◽  
Robert Golub ◽  
Kingo Yamamoto ◽  
...  
Keyword(s):  
Jet Mixing ◽  
Mixing Noise

scholarly journals Integrated circular optical phased array

2021 ◽  
Vol 255 ◽  
pp. 01004
Author(s):  
Qiankun Liu ◽  
Tom Smy ◽  
Ahmad Atieh ◽  
Pavel Cheben ◽  
Alejandro Sánchez-Postigo ◽  
...  
Keyword(s):  
Phased Array ◽  
Field Pattern ◽  
Antenna Element ◽  
Sidelobe Suppression ◽  
Integrated Optical ◽  
Optical Phased Arrays ◽  
Optical Phased Array ◽  
Element Array ◽  
The Individual ◽  
Far Field Pattern

Existing OPAs are typically based on 2D rectangular arrays or 1D linear arrays. Both approaches present a limited field-of-view (FOV) due to the presence of the grating lobes when the element spacing is larger than λ/2. To address the need for an increased steering range, we propose a new design strategy of an OPA system utilizing a 2D circular phased array, with a substantially increased FOV. We present a circular OPA using a demonstrated antenna element design, with an 820-element array. A steering range ΩSR calculated as a solid angle of 0.51π sr, and an angular beamwidth of 0.22°, was achieved. The array exhibits a sidelobe suppression larger than 10 dB, and a FOV of 2π sr. Although the performance is limited by the far field pattern of the individual antenna we chose, our circular OPA achieved, to the best of our knowledge, the largest steering range reported to date compared to the state-of-the-art integrated optical phased arrays reported in literature.

scholarly journals On development of a technique for estimating structural dynamics and strength of modular phased array

2017 ◽  
pp. 75-82
Author(s):  
V. G. Lisovskiy ◽  
E. N. Khmelnitskiy ◽  
A. V. Kuzmicheva
Keyword(s):  
Structural Dynamics ◽  
Phased Array ◽  
Phased Arrays ◽  
Dynamic Environment ◽  
Vibration Acceleration ◽  
Transmission Coefficients ◽  
Mechanical Factors ◽  
Strain Stress ◽  
The Individual ◽  
Stiffening Effect

The purpose of the study was to develop a method of computational and experimental analysis to reduce the dimension of the problem, which makes it possible to simplify and accelerate the strength calculations. When using the method, one can take into account the stiffening effect of the carrier object, where the product will be installed, determine the transmission coefficients of vibration acceleration from the base of the structure to the individual units of the equipment to assess their strength and stability under the influence of mechanical factors. Moreover, the method allows for the strain-stress state analysis using the dynamic environment coefficients. Currently, the developed method is used in the design of several promising projects using modular phased arrays, both sea and land-based

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