Effects of internal waves and turbulence on a horizontal aperture sonar

Henyey, Frank S.; Rouseff, Daniel; Grochocinski, J.M.; Reynolds, Stephen A.; Williams, Kevin L.; Ewart, Terry E.

doi:10.1109/48.585946

Cited by 26 publications

(15 citation statements)

References 19 publications

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“…Though there have been a number of theoretical and numerical studies [e.g. 3,4] that apply these techniques to investigating turbulence in shallow waters, and its influence on acoustic propagation, there have only been a handful of measurements performed [e.g. 5], with a focus on relatively unstratified conditions.…”

Section: Approachmentioning

confidence: 99%

High-Frequency Acoustic Propagation in Shallow, Energetic, Highly-Salt-Stratified Environments

Lavery¹,

Farmer²

2012

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LONG-TERM GOALSThe long term goal of this research is to measure and understand high-frequency, line-of-sight acoustic propagation in an estuarine environment characterized by strong tidal flow, often large salinity stratification, high shear, high dissipation rates of turbulent kinetic energy, shear instabilities, and increased water property variability. OBJECTIVESAcoustic propagation techniques provide a means for remote-sensing of the path-averaged statistical structure and motion of the intervening flow, providing information on the 2-dimensional characteristics of turbulence, microstructure, and advection. Estuaries provide an excellent environment to quantify stratified turbulence and its influence on acoustic propagation as a broad range of stratification and turbulence intensities are encountered within a single tidal cycle.The primary objective is to conduct high-frequency (120 kHz), line-of-sight acoustic propagation measurements from 29 October to 2 November, 2012 in the Connecticut (CT) River estuary. In addition, measurements of high-frequency broadband acoustic backscattering (30 -600 kHz), currents (using a 1.2 MHz ADCP), suspended sediment concentrations, fluorescence, and continuous conductivity, temperature, and depth (CTD) measurements will be performed in order to support the interpretation of the scintillation data. Secondary objectives include testing the validity of the existing theoretical framework for propagation of high-frequency sound through a highly turbulent medium,

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Section: Approachmentioning

confidence: 99%

High-Frequency Acoustic Propagation in Shallow, Energetic, Highly-Salt-Stratified Environments

Lavery¹,

Farmer²

2012

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“…The acoustic propagation sub model is based on the transport theory developed by Dozier and Tappert [1978] augmented to include bottom loss, an important consideration in shallow water. The internal wave sub model is based on a shallow water version of the Garrett-Munk spectrum developed by Henyey et al [1997]. The validity of the combined model is tested by comparison to data from field experiments.…”

Section: Approachmentioning

confidence: 99%

Numerical Modeling of Acoustic Propagation in a Variable Shallow Water Waveguide

Rouseff¹

2006

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Award Number: N00014-04-1-0148 http://www.apl.washington.edu LONG-TERM GOALSRandom variability in shallow water will induce variability in a propagating acoustic field. The general long-term goal of this research is to quantify how random variability in the ocean environment translates into random variability in the acoustic field and the associated signal processing algorithms. The specific long-term goal for the current funding cycle is to develop a predictive capability for the ambient noise notch in the presence of random ocean internal waves. OBJECTIVESThe scientific objective of current effort is to understand the effect of internal waves on the ambient noise notch. The ambient noise notch is a trough in the noise directivity pattern that is observed under certain circumstances. APPROACHThe technical approach to modeling the ambient noise notch is to combine sub models for acoustic propagation, shallow water internal waves, and ambient noise generation. The acoustic propagation sub model is based on the transport theory developed by Dozier and Tappert [1978] augmented to include bottom loss, an important consideration in shallow water. The internal wave sub model is based on a shallow water version of the Garrett-Munk spectrum developed by Henyey et al. [1997]. The validity of the combined model is tested by comparison to data from field experiments. In this testing, we are working with Dajun Tang of APL-UW and using data from the 2001 ASIAEX experiment. WORK COMPLETEDSub models for acoustic propagation, shallow water internal waves, and ambient noise generation were combined to develop a model for the ambient noise notch. In the present funding cycle, a more detailed testing of the model was completed. Model predictions agreed with experimental observations made over extended periods.

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“…The success of the Garrett-Munk (GM) approach [17] in deep water has lead to speculation that a similar model might be useful for shallow water situations. While this remains a research topic [18][19][20], it appears that diffuse background internal waves in shallow water can be represented by a GM-like model. In this section, a spectral model developed from a recent shallow water field experiment is used to specify an ocean internal wave simulator.…”

Section: Effect Of Background Internal Wavesmentioning

confidence: 99%

Effect of shallow water internal waves on ocean acoustic striation patterns

Rouseff

2001

Waves in Random Media

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Contour plots of underwater acoustic intensity, mapped in range and frequency, often exhibit striations. It has been claimed that a scalar parameter "beta," defined in terms of the slope of the striations, is invariant to the details of the acoustic waveguide. In shallow water, the canonical value for beta is one. In the present paper, the waveguide invariant is modeled as a distribution rather than a scalar. The effects of shallow water internal waves on the distribution are studied by numerical simulation. Realizations of time-evolving shallow water internal wave fields are synthesized and acoustic propagation simulated using the parabolic equation method. The waveguide invariant distribution is tracked as the internal wave field evolves in time. Both random background internal waves and more event-like solitary internal waves are considered. Abstract. Contour plots of underwater acoustic intensity, mapped in range and frequency, often exhibit striations. It has been claimed that a scalar parameter "beta," defined in terms of the slope of the striations, is invariant to the details of the acoustic waveguide. In shallow water, the canonical value is ß = 1. In the present paper, the waveguide invariant is modeled as a distribution rather than a scalar. The effects of shallow water internal waves on the distribution are studied by numerical simulation. Realizations of time-evolving shallow water internal wave fields are synthesized and acoustic propagation simulated using the parabolic equation method. The waveguide invariant distribution is tracked as the internal wave field evolves in time. Both random background internal waves and more event-like solitary internal waves are considered.Note: A version of this report was submitted to the journal Waves in Random Media. 097Ocean acoustic striation patterns

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Effects of internal waves and turbulence on a horizontal aperture sonar

Cited by 26 publications

References 19 publications

High-Frequency Acoustic Propagation in Shallow, Energetic, Highly-Salt-Stratified Environments

High-Frequency Acoustic Propagation in Shallow, Energetic, Highly-Salt-Stratified Environments

Numerical Modeling of Acoustic Propagation in a Variable Shallow Water Waveguide

Effect of shallow water internal waves on ocean acoustic striation patterns

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