Near-Field and Far-Field Spectral Analysis of Supersonic Jet with and without Fluidic Injection

2014 ◽  
Author(s):  
Haukur E. Hafsteinsson ◽  
Lars-Erik Eriksson ◽  
Niklas Andersson ◽  
Daniel R. Cuppoletti ◽  
Ephraim J. Gutmark ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Near Field ◽  
Supersonic Jet ◽  
Far Field

Near- and Far-Field Acoustic Measurements for Stepped Nozzles at Over- and Perfectly-Expanded Supersonic Jet Flow Conditions

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
X. F. Wei ◽  
L. P. Chua ◽  
Z. B. Lu ◽  
H. D. Lim ◽  
R. Mariani ◽  
...  
Keyword(s):  
Near Field ◽  
Source Region ◽  
Supersonic Jet ◽  
Jet Flow ◽  
Far Field ◽  
Acoustic Measurements ◽  
Flow Conditions ◽  
Spectra Analysis ◽  
Highly Sensitive ◽  
Nozzle Configuration

Abstract Detailed near- and far-field acoustic measurements were conducted for two circular stepped nozzles with 30 deg and 60 deg design inclinations at over- and perfectly-expanded supersonic jet flow conditions and compared to those for a circular nonstepped nozzle. Far-field acoustic results show that stepped nozzles play an insignificant role in altering noise emissions at perfectly expanded condition. At an over-expanded condition, however, the longer stepped nozzle produces significant noise reductions at the sideline and upstream quadrants, while the shorter stepped nozzle does not. Noise spectra analysis and Schlieren visualizations show that noise reduction can be primarily attributed to mitigations in the broadband shock-associated noise (BSAN), due to the ability of the longer stepped nozzle in suppressing shock strengths at downstream region. Near-field acoustic measurements reveal that the source region, as well as the intensity of turbulent and shock noises, are highly sensitive to the stepped nozzle configuration. Furthermore, BSAN seems to be eliminated by the longer stepped nozzle in near-field region due to the shock structure modifications.

Measurement of Near-Field and Far-Field Noise From Full Scale High Performance Jet Engines

2010 ◽  
Author(s):  
Richard McKinley ◽  
Robert McKinley ◽  
Kent Gee ◽  
Tony Pilan ◽  
Frank Mobley ◽  
...  
Keyword(s):  
High Performance ◽  
Noise Exposure ◽  
Near Field ◽  
Broad Band ◽  
Supersonic Jet ◽  
Full Scale ◽  
Far Field ◽  
Jet Engine ◽  
Field Noise ◽  
Non Linear Propagation

Accurate measurement of the noise fields emitted by a full scale high performance jet engine and jet plume (with supersonic jet flow) requires detailed planning and careful execution. The apparent acoustic source can be very large, more than 50 feet long and 20 feet high and wide. The jet plume contains many noise generating sources, the main two being shock (broad band and shock cells) and turbulent mixing. This paper is an initial description of a detailed method to accurately measure and describe the near-field noise while simultaneously measuring the far-field noise. For a large high performance jet engine, the acoustic far-field may not be formed until more than 1000 ft away from the plume. The paper also describes proposed methods to measure the non-linear propagation of the noise from the near-field to the far-field. The proposed methodology described with vetting will be considered as an US military standard (MILSTD) with possible later consideration as American standard measurement technique to describe noise fields for personnel noise exposure and for measuring the performance of jet engine noise reduction technologies.

Global modes and transient response of a cold supersonic jet

2011 ◽  
Vol 669 ◽  
pp. 225-241 ◽  
Author(s):  
JOSEPH W. NICHOLS ◽  
SANJIVA K. LELE
Keyword(s):  
Acoustic Radiation ◽  
Near Field ◽  
Supersonic Jet ◽  
Mode Analysis ◽  
Wave Radiation ◽  
Far Field ◽  
Transient Growth ◽  
Global Mode ◽  
Laminar Jet ◽  
Global Modes

Global-mode analysis is applied to a cold, M = 2.5 laminar jet. Global modes of the non-parallel jet capture directly both near-field dynamics and far-field acoustics which, in this case, are coupled by Mach wave radiation. In addition to type (a) modes corresponding to Kelvin–Helmholtz instability, it is found that the jet also supports upstream-propagating type (b) modes which could not be resolved by previous analyses of the parabolized stability equations. The locally neutrally propagating part of a type (a) mode consists of the growth and decay of an aerodynamic wavepacket attached to the jet, coupled with a beam of acoustic radiation at a low angle to the jet downstream axis. Type (b) modes are shown to be related to the subsonic family of modes predicted by Tam & Hu (1989). Finally, significant transient growth is recovered by superposing damped, but non-normal, global modes, leading to a novel interpretation of jet noise production. The mechanism of optimal transient growth is identified with a propagating aerodynamic wavepacket which emits an acoustic wavepacket to the far field at an axial location consistent with the peaks of the locally neutrally propagating parts of type (a) modes.

Magnetic Tag Antenna for UHF Near-field and Far-Field RFID Applications

2015 ◽  
Vol 5 (2) ◽  
pp. 119
Author(s):  
Mondher Dhaouadi ◽  
M. Mabrouk ◽  
T. Vuong ◽  
A. Ghazel
Keyword(s):  
Near Field ◽  
Far Field ◽  
Rfid Applications

Far field modeling of the Mamala Bay outfalls

1998 ◽  
Vol 38 (10) ◽  
pp. 323-330
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Field Model ◽  
Near Field ◽  
Far Field ◽  
Field Modeling ◽  
Visitation Frequency ◽  
Statistical Variation ◽  
Long Time ◽  
Harmonic Average ◽  
Ocean Outfall ◽  
Acoustic Doppler Current Profilers

The results of far field modeling of the wastefield formed by the Sand Island, Honolulu, ocean outfall are presented. A far field model, FRFIELD, was coupled to a near field model, NRFIELD. The input data for the models were long time series of oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers and density stratification measured by thermistor strings. Thousands of simulations were made to predict the statistical variation of wastefield properties around the diffuser. It was shown that the visitation frequency of the wastefield decreases rapidly with distance from the diffuser. The spatial variation of minimum and harmonic average dilutions was also predicted. Average dilution increases rapidly with distance. It is concluded that any impact of the discharge will be confined to a relatively small area around the diffuser and beach impacts are not likely to be significant.

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