Predictability of acoustic intensity and horizontal wave numbers in shallow water at low frequencies using parabolic approximations

1993 ◽  
Vol 94 (2) ◽  
pp. 1034-1043 ◽  
Author(s):  
R. J. Cederberg ◽  
W. L. Siegmann ◽  
M. J. Jacobson ◽  
W. M. Carey
Keyword(s):  
Shallow Water ◽  
Acoustic Intensity ◽  
Low Frequencies ◽  
Wave Numbers ◽  
Horizontal Wave

Predictability of acoustic intensity in shallow water at low frequencies using parabolic approximations

1991 ◽  
Vol 89 (4B) ◽  
pp. 1896-1896 ◽  
Author(s):  
R. J. Cederberg ◽  
W. L. Seigmann ◽  
M. J. Jacobson ◽  
W. M. Carey
Keyword(s):  
Shallow Water ◽  
Acoustic Intensity ◽  
Low Frequencies

PARAMETER SENSITIVITIES IN TWO-LAYER ISOSPEED MODELS OF SHALLOW WATER CHANNELS

1993 ◽  
Vol 01 (04) ◽  
pp. 469-486 ◽  
Author(s):  
R. J. CEDERBERG ◽  
W. L. SIEGMANN ◽  
M. J. JACOBSON ◽  
W. M. CAREY
Keyword(s):  
Shallow Water ◽  
Low Frequency ◽  
Propagation Model ◽  
Wave Number ◽  
Parameter Uncertainties ◽  
Rates Of Change ◽  
Wave Numbers ◽  
Analytic Expressions ◽  
Horizontal Wave ◽  
Order Of Magnitude

Sensitivities of relative intensity, interference wavelength, and horizontal wave number predictions to input parameters in two-layer isospeed models of shallow-water, low-frequency (less than 100 Hz) acoustic propagation problems are examined. The investigation is directed toward environmental parameter values corresponding generally to those near the site of a recent New Jersey shelf experiment. Typical parameter uncertainties in the environment of the experiment site are used to determine effects of parameter sensitivities on the accuracy of propagation model predictions. Also, analytic expressions for rates of change of wave numbers with respect to parameters are used to compute wave number and interference wavelength changes caused by parameter variations corresponding to the uncertainties. It is found that channel depth variations cause the largest change in intensity, while water sound speed variations have the greatest effect on wave numbers. Variabilities of the parameter sensitivities in regions about the base parameter sets are also examined, with the rates of change generally staying of the same order of magnitude throughout the regions considered. However, wave numbers which are close to cutoff can produce rates of change which vary by as much as three orders of magnitude.

Experimental Study of Slow-Drift Ship Motions in Shallow Water Random Waves

2011 ◽  
Author(s):  
Carl Trygve Stansberg ◽  
Trygve Kristiansen
Keyword(s):  
Spectral Analysis ◽  
Shallow Water ◽  
Transfer Functions ◽  
Second Order ◽  
Ship Motions ◽  
Random Wave ◽  
Random Waves ◽  
Low Frequencies ◽  
Wave Basin ◽  
Drift Forces

Slowly varying motions and drift forces of a large moored ship in random waves at 35m water depth are investigated by an experimental wave basin study in scale 1:50. A simple horizontal mooring set-up is used. A second-order wave correction is applied to minimize “parasitic” long waves. The effect on the ship motion from the correction is clearly seen, although less in random wave spectra than in pure bi-chromatic waves. Empirical quadratic transfer functions (QTFs) of the surge drift force are found by use of cross-bi-spectral analysis, in two different spectra have been obtained. The QTF levels increase significantly with lower wave frequencies (except at the diagonal), which is special for finite and shallow water. Furthermore, the QTF levels frequencies at low frequencies increase significantly out from the QTF diagonal. Thus Newman’s approximation should preferrably not be used in these cases. Using the LF waves as a direct excitation in a “linear” ship force analysis gives random records that compare reasonably well with those from the cross-bi-spectral analysis. This confirms the idea that the drift forces in shallow water are closely correlated to the second-order potential, and thereby by the second-order LF waves.

scholarly journals A Prediction Method for Acoustic Intensity Vector Field of Elastic Structure in Shallow Water Waveguide

2020 ◽  
Vol 2020 ◽  
pp. 1-23
Author(s):  
Wenbo Wang ◽  
Desen Yang ◽  
Jie Shi
Keyword(s):  
Spatial Structure ◽  
Shallow Water ◽  
Transfer Functions ◽  
Source Parameters ◽  
Prediction Method ◽  
Sound Field ◽  
Elastic Structure ◽  
Superposition Method ◽  
Acoustic Intensity ◽  
Sound Energy

Compared with scalar sound field, vector sound field explained the spatial structure of sound field better since it not only presents the sound energy distribution but also describes the sound energy flow characteristics. Particularly, with more complicated interaction among different wavefronts, the vector sound field characteristics of an elastic structure in a shallow water waveguide are worthy of studying. However, there is no reliable prediction method for the vector sound field of an elastic structure with a high efficiency in a shallow water waveguide. To solve the problem, transfer functions in the waveguide have been modified with some approximations to apply for the vector sound field prediction of elastic structures in shallow water waveguides. The method is based on the combined wave superposition method (CWSM), which has been proved to be efficient for predicting scalar sound field. The rationality of the approximations is validated with simulations. Characteristics of the complex acoustic intensity, especially the vertical components are observed. The results show that, with constructive and destructive interferences in the depth direction, there could be quantities of crests and vortices in the spatial structure of time-dependent complex intensity, which manifest a unique dynamic characteristic of sound energy. With more complicated interactions among the wavefronts, a structure source could not be equivalent to a point source in most instances. The vector sound field characteristics of the two sources could be entirely different, even though the scalar sound field characteristics are similar. Meanwhile, source types, source parameters, ocean environment parameters, and geo parameters may have influence on the vector sound field characteristics, which could be explained with the normal mode theory.

Acoustic intensity fluctuations induced by internal waves in a shallow‐water waveguide

1996 ◽  
Vol 100 (4) ◽  
pp. 2666-2666
Author(s):  
Steven Finette ◽  
Altan Turgut ◽  
John Apel
Keyword(s):  
Shallow Water ◽  
Internal Waves ◽  
Acoustic Intensity ◽  
Intensity Fluctuations

Sediment sound speed inversion at low frequencies in shallow water

2017 ◽  
Vol 142 (4) ◽  
pp. 2621-2621
Author(s):  
Zoi-Heleni Michalopoulou
Keyword(s):  
Shallow Water ◽  
Sound Speed ◽  
Low Frequencies

Shallow Water Internal Waves and Associated Acoustic Intensity Fluctuations

2006 ◽  
Vol 56 (4) ◽  
pp. 485-493 ◽  
Author(s):  
P.V. Hareesh Kumar ◽  
K.V. Sanilkumar ◽  
V.N. Panchalai
Keyword(s):  
Shallow Water ◽  
Internal Waves ◽  
Acoustic Intensity ◽  
Intensity Fluctuations
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