Long-range propagation of nonlinear infrasound waves through an absorbing atmosphere

TitleLong-range propagation of nonlinear infrasound waves through an absorbing atmosphere
Publication TypeJournal Article
Year of Publication2016
Authorsde Groot-Hedlin C.D
JournalJournal of the Acoustical Society of America
Date Published2016/04
Type of ArticleArticle
ISBN Number0001-4966
Accession NumberWOS:000374974900011
Keywordsabsorption; bolides; equations; finite-difference; gravity waves; media; model; navier-stokes; numerical-simulation

The Navier-Stokes equations are solved using a finite-difference, time-domain (FDTD) approach for axi-symmetric environmental models, allowing three-dimensional acoustic propagation to be simulated using a two-dimensional Cylindrical coordinate system. A method to stabilize the FDTD algorithm in a viscous medium at atmospheric densities characteristic of the lower thermosphere is described. The stabilization scheme slightly alters the governing equations but results in quantifiable dispersion characteristics. It is shown that this method leaves sound speeds and attenuation unchanged at frequencies that are well resolved by the temporal sampling rate but strongly attenuates higher frequencies. Numerical experiments are performed to assess the effect of source strength on the amplitudes and spectral content of signals recorded at ground level at a range of distances from the source. It is shown that the source amplitudes have a stronger effect on a signal's dominant frequency than on its amplitude. Applying the stabilized code to infrasound propagation through realistic atmospheric profiles shows that nonlinear propagation alters the spectral content of low amplitude thermospheric signals, demonstrating that nonlinear effects are significant for all detectable thermospheric returns. (C) 2016 Acoustical Society of America.

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