Horizontal Lloyd mirror patterns from straight and curved nonlinear internal waves

McMahon, Kara G.; Reilly‐Raska, Laurel K.; Siegmann, William L.; Lynch, James F.; Duda, Timothy F.

doi:10.1121/1.3666004

Cited by 16 publications

(21 citation statements)

References 26 publications

(43 reference statements)

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“…(1) Nonlinear internal wave effects • If an acoustic mode propagates adiabatically across a nonlinear internal wave (NIW) at small incident angles with the wave front, the interaction may produce horizontal Lloyd mirror interference patterns [8], as predicted by other researchers and observed recently, and the patterns have especially interesting features when the NIW front has curvature.…”

Section: Work Completedmentioning

confidence: 90%

Shallow Water Propagation

Siegmann¹,

McMahon²

2012

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LONG-TERM GOALSDevelop methods for deterministic and stochastic acoustic calculations in complex shallow water environments, specify their capabilities and accuracy, and apply them to explain experimental data and understand physical mechanisms of propagation. OBJECTIVES(A) Treat propagation from narrowband and broadband sources over elastic and poro-elastic sediments, and incorporate realistic bathymetric, topographic, and geoacoustic variations. (B) Construct representations for ocean environmental and geoacoustic variability using data and parametric models. Determine acoustic fields with PE, normal mode, and other approximation methods. Use experimental data and computational results to assess propagation mechanisms.

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Section: Work Completedmentioning

confidence: 90%

Shallow Water Propagation

Siegmann¹,

McMahon²

2012

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“…al. [18] to describe the effects of horizontal acoustic ducting in between internal waves and by McMahon for theoretical studies of Horizontal Lloyds Mirror effect [41]. In the following sections, we will consider three-dimensional mode coupling The SIA has an advantage of its simplicity as it replaces the problem of continuous modal refraction and coupling with discrete modal refraction and coupling at several vertical interfaces.…”

Section: Sharp Interface Approximationmentioning

confidence: 99%

“…Analysis of multiple SAR images, including this example suggests that the angle of the waves cross varies widely from 0 to 90 degrees. Although curvature of the internal wave fronts is commonly observed together with the wave crossings, in this chapter we will study the effects of three-dimensional acoustic propagation through the medium that contains crossing of straight wave trains (acoustical effects caused by the wave curvature are studied in [41,17]). In particular, we are interested in the interaction of the acoustic energy ducted in between waves from one train with crossing wave train.…”

Section: Chapter 6 Crossing Internal Wavesmentioning

confidence: 99%

Three-dimensional acoustic propagation through shallow water internal, surface gravity and bottom sediment waves

Shmelev¹

2011

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This thesis describes the physics of fully three-dimensional low frequency acoustic interaction with internal waves, bottom sediment waves and surface swell waves that are often observed in shallow waters and on continental slopes. A simple idealized model of the ocean waveguide is used to analytically study the properties of acoustic normal modes and their perturbations due to waves of each type. The combined approach of a semi-quantitative study based on the geometrical acoustics approximation and on fully three-dimensional coupled mode numerical modeling is used to examine the azimuthal dependence of sound wave horizontal reflection from, transmission through and ducting between straight parallel waves of each type. The impact of the natural crossings of nonlinear internal waves on horizontally ducted sound energy is studied theoretically and modeled numerically using a three-dimensional parabolic equation acoustic propagation code. A realistic sea surface elevation is synthesized from the directional spectrum of long swells and used for three-dimensional numerical modeling of acoustic propagation. As a result, considerable normal mode amplitude scintillations were observed and shown to be strongly dependent on horizontal azimuth, range and mode number. Full field numerical modeling of low frequency sound propagation through large sand waves located on a sloped bottom was performed using the high resolution bathymetry of the mouth of San Francisco Bay. Very strong acoustic ducting is shown to steer acoustic energy beams along the sand wave's curved crests.

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“…Figures 4 and 5 illustrate fields used in process studies of sound in isolated strong internal waves. Process studies, showing interesting results regarding the structure of ducted and redirected sound energy, are numerous (Badiey et al 2011;McMahon et al 2012;Lin et al 2013b). …”

Section: E Analytic Feature Model and Acoustics Modelmentioning

confidence: 99%

Modeling and Forecasting Ocean Acoustic Conditions

Duda¹

2017

j mar res

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Modeling acoustic conditions in an oceanic environment is a multiple-step process. The environmental conditions (features) in the area first must be measured or estimated; relevant features include seabed geometry, seabed composition, and four-dimensionally (4D) variable sound-speed and density variations related to evolving or wave motions. Often the dynamical wave modeling depends on first obtaining correct seabed and mean stratification conditions (for example, nonlinear internal wave modeling). Next, this information must be included in sound propagation modeling. A selection of the many methods and tools available for these tasks are described, with a focus on modeling sounds of 20 to 1000 Hz propagating through water-column features that are time-dependent and variable in three dimensions (i.e., 4D variable). An example of a 3D parabolic equation acoustic calculation shows how variability caused by evolving internal tidal waves affects sound propagation. Different propagation and scattering regimes are discussed, including the theoretically delineated weak scattering and strong scattering regimes, as well as the empirically examined regime found in nonlinear internal waves. The histories and the current state of our oceanographic knowledge (the input to acoustic modeling) and of our ability to effectively model complex acoustic conditions are discussed. Example acoustic simulation applications are also discussed; these are ocean acoustic tomography, coherence prediction, and signal-to-noise ratio prediction. Types of ocean models and acoustic models and how they are interfaced are also examined. These include deterministic, statistical analytic feature models.

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Horizontal Lloyd mirror patterns from straight and curved nonlinear internal waves

Cited by 16 publications

References 26 publications

Shallow Water Propagation

Shallow Water Propagation

Three-dimensional acoustic propagation through shallow water internal, surface gravity and bottom sediment waves

Modeling and Forecasting Ocean Acoustic Conditions

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