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Transition scattering in stochastically inhomogeneous media
The Journal of the Acoustical Society of America
|February 12, 2009
Summary
Acoustic transition scattering occurs in nonhomogeneous media even at subsonic speeds. This phenomenon arises from the source field scattering on medium inhomogeneities, creating acoustic radiation.
Area of Science:
- Acoustics
- Wave Propagation
- Fluid Dynamics
Background:
- Acoustic radiation typically involves Mach shock waves when source velocity exceeds sonic speed in homogeneous media.
- In nonhomogeneous or nonstationary media, transition radiation (diffraction/scattering) can occur even at subsonic velocities.
Purpose of the Study:
- To establish key features of acoustical transition scattering in media with fluctuating acoustic parameters.
- To analytically investigate the formation and physical mechanisms of transition radiation.
Main Methods:
- Utilized the Green's function method with functional derivatives for analytical study.
- Determined the wave number-frequency relationship (k=k(omega)) for acoustic waves.
Main Results:
- Identified key features of acoustical transition scattering in fluctuating media.
- Established phasing conditions for transition scattering and Cherenkov radiation.
- Provided a physical explanation: scattering of the source field on medium inhomogeneities.
Conclusions:
- Transition radiation is a result of the source's attached acoustic field readjusting to equilibrium after deformation by medium fluctuations.
- This scattering mechanism explains the formation of acoustic radiation in nonhomogeneous media at subsonic speeds.
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