Tracing Three-Dimensional Acoustic Wavefronts in Inhomogeneous, Moving Media

Zabotin, N. A.; Godin, Oleg A.; Sava, Paul; Zabotina, Liudmila

doi:10.1142/s0218396x14500027

Cited by 4 publications

(2 citation statements)

References 51 publications

(84 reference statements)

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“…The WAM description of the atmosphere above southern Iceland, which is shown in figure 2(a), was previously used in modelling long-range propagation of atmospheric waves generated by the 2010 eruption of Eyjafjallajökull volcano (Matoza et al 2011;Zabotin et al 2014). Note that below about 250 km the effective buoyancy frequency N 0 , which enters the AGW dispersion relation (3.5), varies much more smoothly with height than the buoyancy frequency N (figure 2b).…”

Section: Derivation Based On the Wave Equation For Lagrangian Pressurmentioning

confidence: 99%

Wentzel–Kramers–Brillouin approximation for atmospheric waves

Godin

2015

J. Fluid Mech.

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Ray and Wentzel-Kramers-Brillouin (WKB) approximations have long been important tools in understanding and modelling propagation of atmospheric waves. However, contradictory claims regarding the applicability and uniqueness of the WKB approximation persist in the literature. Here, we consider linear acoustic-gravity waves (AGWs) in a layered atmosphere with horizontal winds. A self-consistent version of the WKB approximation is systematically derived from first principles and compared to ad hoc approximations proposed earlier. The parameters of the problem are identified that need to be small to ensure the validity of the WKB approximation. Properties of low-order WKB approximations are discussed in some detail. Contrary to the better-studied cases of acoustic waves and internal gravity waves in the Boussinesq approximation, the WKB solution contains the geometric, or Berry, phase. The Berry phase is generally non-negligible for AGWs in a moving atmosphere. In other words, knowledge of the AGW dispersion relation is not sufficient for calculation of the wave phase.

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Section: Derivation Based On the Wave Equation For Lagrangian Pressurmentioning

confidence: 99%

Wentzel–Kramers–Brillouin approximation for atmospheric waves

Godin

2015

J. Fluid Mech.

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“…Ñ20mpÝ? (Ø?nØŠ †pdÅå(GBTµGaussian beam tracing)OŽ(J3^_6•• é'" º [25,26] Ú|^(Å5 O¿ ¿ þ [27] "º|éÅcÚ(‚; K•©z [7,8]®²‰Ñ ©Û §AO…”

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confidence: 99%

Gaussian beam tracing for three-dimensional sound propagation problems in subsonic moving medium

Chen¹,

Zhang²,

Ming-Hui³

et al. 2023

Acta Phys. Sin.

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The study of sound propagation in moving media is important in various fields, such as aeroacoustics and underwater acoustics. To address this problem, a three-dimensional Gaussian beam tracing model has been developed for subsonic moving media, based on the Helmholtz equation of velocity potential for high-frequency sound wave in a moving medium with arbitrary Mach numbers. By using the beam tracing method, the dynamic ray equations in the moving medium are derived, and the partial differential equation is replaced with ordinary differential equations, allowing for a more efficient and accurate calculation of the three-dimensional sound field in the moving medium. The Gaussian beam tracing method reveals that the expansion of the beam in a moving medium is more complex than in a static medium, and the energy in the ray tube is not necessarily conserved. The model has been applied to several problems, including point source sound propagation in semi-infinite homogeneous media, three-dimensional long-range sound propagation in horizontally layered atmospheres, and three-dimensional sound propagation in the Gulf Stream. The results of the point source sound propagation problem in the semi-infinite homogeneous medium verify the effectiveness and accuracy of the model. The results of the atmospheric sound propagation problem indicate that compared with the commonly used N@2D method, the three-dimensional Gaussian beam tracing in a moving medium fully considers the effect of medium motion, especially the effect of crosswind, and can calculate the sound pressure field more accurately. Although the Mach number of the ocean current is very small, its effect cannot be ignored and can quantitatively change the sound propagation mode and affect the convergence zone position. In some areas, the difference between considering and not considering the ocean current is more than 5dB. Moreover, the deviation of rays caused by lateral flow is much smaller and requires interface reflection to show more obvious deviation, and the impact of lateral flow on sound propagation is much smaller compared to the impact brought by flow velocity parallel to the propagation direction. In conclusion, the developed Gaussian beam tracing method provides an accurate and efficient approach to solve the sound propagation problem in subsonic moving media.

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Dissipation of acoustic-gravity waves: An asymptotic approach

Godin

2014

The Journal of the Acoustical Society of America

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Acoustic-gravity waves in the middle and upper atmosphere and long-range propagation of infrasound are strongly affected by air viscosity and thermal conductivity. To characterize the wave dissipation, it is typical to consider idealized environments, which admit plane-wave solutions. Here, an asymptotic approach is developed that relies instead on the assumption that spatial variations of environmental parameters are gradual. It is found that realistic assumptions about the atmosphere lead to rather different predictions for wave damping than do the plane-wave solutions. A modification to the Sutherland-Bass model of infrasound absorption is proposed.

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Tracing Three-Dimensional Acoustic Wavefronts in Inhomogeneous, Moving Media

Cited by 4 publications

References 51 publications

Wentzel–Kramers–Brillouin approximation for atmospheric waves

Wentzel–Kramers–Brillouin approximation for atmospheric waves

Gaussian beam tracing for three-dimensional sound propagation problems in subsonic moving medium

Dissipation of acoustic-gravity waves: An asymptotic approach

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