Acoustic Aperture Diffraction in a Transversely Moving Medium

1977 ◽  
pp. 611-630
Author(s):  
G. Flesher ◽  
S. Elliott
Keyword(s):  
Moving Medium ◽  
Aperture Diffraction

The Temperature Function in a Moving Medium

1951 ◽  
Vol 22 (11) ◽  
pp. 1389-1389 ◽  
Author(s):  
R. H. Ritchie
Keyword(s):  
Moving Medium ◽  
Temperature Function

ON THE THEORY OF THE DOPPLER EFFECT IN A MOVING MEDIUM

1998 ◽  
Vol 13 (01) ◽  
pp. 1-6 ◽  
Author(s):  
BRUNO BERTOTTI
Keyword(s):  
Solar Wind ◽  
Doppler Effect ◽  
Dispersive Medium ◽  
Time Derivative ◽  
Optical Path ◽  
Moving Medium ◽  
Perturbation Theorem ◽  
Hamiltonian Theory ◽  
The Doppler Effect ◽  
Definition Of

The increase in the accuracy of Doppler measurements in space requires a rigorous definition of the observed quantity when the propagation occurs in a moving, and possibly dispersive medium, like the solar wind. This is usually done in two divergent ways: in the phase viewpoint it is the time derivative of the correction to the optical path; in the ray viewpoint the signal is obtained form the deflection produced in the ray. They can be reconciled by using the time derivative of the optical path in the Lagrangian sense, i.e. differentiating from ray to ray. To rigorously derive this result an understanding, through relativistic Hamiltonian theory, of the delicate interplay between rays and phase is required; a general perturbation theorem which generalizes the concept of the Doppler effect as a Lagrangian derivative is proved. Relativistic retardation corrections O(v) are obtained, well within the expected sensitivity of Doppler experiments near solar conjunction.

Ultra-precision detection of surface defects of large aperture diffraction grating based on machine vision

2021 ◽  
Author(s):  
Haotian Wang ◽  
Chaoming Li ◽  
Xinrong Chen ◽  
Zhe Huang ◽  
Jiayao Pan ◽  
...  
Keyword(s):  
Machine Vision ◽  
Diffraction Grating ◽  
Surface Defects ◽  
Large Aperture ◽  
Ultra Precision ◽  
Aperture Diffraction

scholarly journals A Finite-Difference Wavenumber-Time Domain Method for Sound Field Prediction in a Uniformly Moving Medium

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Bichun Dong ◽  
Runmei Zhang ◽  
Chuanyang Yu ◽  
Huan Li
Keyword(s):  
Finite Difference ◽  
Time Domain ◽  
Sound Pressure ◽  
Sound Field ◽  
Time Domain Method ◽  
Practical Significance ◽  
Moving Medium ◽  
Domain Method ◽  
Aero Engines ◽  
The Stability

Sound field prediction has practical significance in the control of noise generated by sources in a flow, for example, the noise in aero-engines and ventilation systems. Aiming at accurate and flexible prediction of time-dependent sound field, a finite-difference wavenumber-time domain method for sound field prediction in a uniformly moving medium is proposed. The method is based on the second-order convective wave equation, and the wavenumber-time domain representation of the sound pressure field on one plane is forward propagated via a derived recursive expression. In this paper, the recursive expression is first deduced, and then numerical stability and dispersion of the proposed method are analyzed, based on which the stability condition is given and the correction of dispersion related to the transition frequency is made. Numerical simulations are conducted to test the performance of the proposed method, and the results show that the method is valid and robust at different Mach numbers.

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