Sound-wave coherence in atmospheric turbulence with intrinsic and global intermittency

The coherence function of sound waves propagating through an intermittently turbulent atmosphere is calculated theoretically. Intermittency mechanisms due to both the turbulent energy cascade (intrinsic intermittency) and spatially uneven production (global intermittency) are modeled using ensembles...

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Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2008-08, Vol.124 (2), p.743-757
Main Authors: Wilson, D. Keith, Ostashev, Vladimir E., Goedecke, George H.
Format: Article
Language:English
Subjects:
Acoustics
Aeroacoustics, atmospheric sound
Atmospheric Pressure
Computer Simulation
Exact sciences and technology
Fundamental areas of phenomenology (including applications)
Markov Chains
Models, Theoretical
Motion
Normal Distribution
Physics
Reproducibility of Results
Sound
Temperature
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Summary:The coherence function of sound waves propagating through an intermittently turbulent atmosphere is calculated theoretically. Intermittency mechanisms due to both the turbulent energy cascade (intrinsic intermittency) and spatially uneven production (global intermittency) are modeled using ensembles of quasiwavelets (QWs), which are analogous to turbulent eddies. The intrinsic intermittency is associated with decreasing spatial density (packing fraction) of the QWs with decreasing size. Global intermittency is introduced by allowing the local strength of the turbulence, as manifested by the amplitudes of the QWs, to vary in space according to superimposed Markov processes. The resulting turbulence spectrum is then used to evaluate the coherence function of a plane sound wave undergoing line-of-sight propagation. Predictions are made by a general simulation method and by an analytical derivation valid in the limit of Gaussian fluctuations in signal phase. It is shown that the average coherence function increases as a result of both intrinsic and global intermittency. When global intermittency is very strong, signal phase fluctuations become highly non-Gaussian and the average coherence is dominated by episodes with weak turbulence.
ISSN:0001-4966
1520-8524
DOI:10.1121/1.2945162