Tones in the Acoustic Far Field of Jets in the Upstream Direction

AIAA Journal ◽  
2021 ◽  
pp. 1-10
Author(s):  
Christophe Bogey
Keyword(s):  
Far Field ◽  
Upstream Direction

A model supersonic buried-nozzle jet: instability and acoustic wave scattering and the far-field sound

2015 ◽  
Vol 778 ◽  
pp. 189-215 ◽  
Author(s):  
Arnab Samanta ◽  
Jonathan B. Freund
Keyword(s):  
Far Field ◽  
Sound Waves ◽  
Vortex Sheets ◽  
Instability Waves ◽  
Acoustic Wave Scattering ◽  
Instability Modes ◽  
Source Mechanisms ◽  
Upstream Direction ◽  
Field Radiation ◽  
Hopf Method

We consider sound source mechanisms involving the acoustic and instability modes of dual-stream isothermal supersonic jets with the inner nozzle buried within an outer shroud-like nozzle. A particular focus is scattering into radiating sound waves at the shroud lip. For such jets, several families of acoustically coupled instability waves exist, beyond the regular vortical Kelvin–Helmholtz mode, with different shapes and propagation characteristics, which can therefore affect the character of the radiated sound. In our model, the coaxial shear layers are vortex sheets while the incident acoustic disturbances are the propagating shroud modes. The Wiener–Hopf method is used to compute their scattering at the sharp shroud edge to obtain the far-field radiation. The resulting far-field directivity quantifies the acoustic efficiency of different mechanisms, which is particularly important in the upstream direction, where the results show that the scattered sound is more intense than that radiated directly by the shear-layer modes.

EFFECT OF FAR-FIELD FLOW ON THE GROWTH OF COLUMNAR CRYSTAL IN TERNARY UNDERCOOLED MELT

2019 ◽  
Vol 27 (07) ◽  
pp. 1950170
Author(s):  
HAILONG FAN ◽  
MINGWEN CHEN ◽  
YANYAN SHAN
Keyword(s):  
Deflection Angle ◽  
Impurity Content ◽  
Far Field ◽  
Columnar Crystal ◽  
Approximate Analytical Expression ◽  
Interface Growth ◽  
Upstream Direction ◽  
Undercooled Melt ◽  
Growth Problem ◽  
Heat Transport Process

The asymptotic method has been used to investigate the columnar crystals growth subjected to far-field flow in ternary undercooled melt under non-isothermal conditions, and approximate analytical expression of radius and interface growth rate of columnar crystals growth have been given. It is found that the flow causes columnar crystal to grow faster in the upstream direction and slower in the downstream direction, and the growth of columnar crystals in flowing ternary melt is also affected by impurity content, that is, the higher the impurity content, the faster the columnar crystal grows in the upstream direction and the slower the growth in the downstream direction. The growth problem of columnar crystals from multi-component melt under flow is more complicated than that of a pure melt because it involves both the heat transport process and mass transport in the solute. The results show that the deflection angle of columnar crystals is a result of interaction of flow and impurity content.

Possible applications of fraunhofer holography in high resolution electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 222-223 ◽  
Author(s):  
N. Bonnet ◽  
M. Troyon ◽  
P. Gallion
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Transfer Function ◽  
Radiation Damage ◽  
High Resolution Electron Microscopy ◽  
Far Field ◽  
Field Region ◽  
Crystalline Materials ◽  
Resolution Electron ◽  
The Ideal

Two main problems in high resolution electron microscopy are first, the existence of gaps in the transfer function, and then the difficulty to find complex amplitude of the diffracted wawe from registered intensity. The solution of this second problem is in most cases only intended by the realization of several micrographs in different conditions (defocusing distance, illuminating angle, complementary objective apertures…) which can lead to severe problems of contamination or radiation damage for certain specimens.Fraunhofer holography can in principle solve both problems stated above (1,2). The microscope objective is strongly defocused (far-field region) so that the two diffracted beams do not interfere. The ideal transfer function after reconstruction is then unity and the twin image do not overlap on the reconstructed one.We show some applications of the method and results of preliminary tests.Possible application to the study of cavitiesSmall voids (or gas-filled bubbles) created by irradiation in crystalline materials can be observed near the Scherzer focus, but it is then difficult to extract other informations than the approximated size.

Multifunctional far-field luminescence nanoscope for studying single molecules and quantum dots

2018 ◽  
Vol 189 (03) ◽  
pp. 312-322 ◽  
Author(s):  
Ivan Yu. Eremchev ◽  
M.Yu. Eremchev ◽  
Andrei V. Naumov
Keyword(s):  
Quantum Dots ◽  
Single Molecules ◽  
Far Field

Conservative Estimation of Whole-body Average SAR in Infant Model for 0.3-6GHz Far-Field Exposure

2009 ◽  
Vol 129 (12) ◽  
pp. 2102-2107 ◽  
Author(s):  
Akimasa Hirata ◽  
Yoshio Nagaya ◽  
Naoki Ito ◽  
Osamu Fujiwara ◽  
Tomoaki Nagaoka ◽  
...  
Keyword(s):  
Whole Body ◽  
Far Field ◽  
Field Exposure ◽  
Conservative Estimation
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