scholarly journals THREE-DIMENSIONAL ACOUSTIC SIMULATION OF AN ACOUSTIC REFRACTION BY A NONLINEAR INTERNAL WAVE IN A WEDGE BATHYMETRY

2010 ◽  
Vol 18 (03) ◽  
pp. 279-296 ◽  
Author(s):  
LINUS Y. S. CHIU ◽  
ANDREA Y. Y. CHANG ◽  
CHI-FANG CHEN ◽  
RUEY-CHANG WEI ◽  
YING-JANG YANG ◽  
...  
Keyword(s):  
Internal Wave ◽  
Transmission Loss ◽  
Three Dimensional ◽  
Joint Effect ◽  
Acoustic Mode ◽  
Acoustic Energy ◽  
Acoustic Effect ◽  
Nonlinear Internal Wave ◽  
Mode Amplitude ◽  
Whispering Gallery

Nonlinear internal wave (NIW) results in three dimensional acoustic effect such as ducting and whispering gallery effects in acoustic propagation. Acoustic energy restricted within internal wave crests (crest–crest) on the shelf constitutes the ducting effect, and energy confined along the crest when the source is located upslope from the NIW crest is known as the whispering gallery effect. Numerical experiments are presented in this paper for the study of 3D acoustic effects caused by both internal wave and wedge-bathymetry. 3D effects are predicted by Wide-Angle-FOR3D and the modal contents are calculated by MOS3DPEF. Following are the case studies detailing differences between 2D and 3D calculation, and the joint effect of propagating internal waves with upslope-bathymetry. Modeled time series of transmission Loss reveal that internal wave induces the oceanic waveguide and concentrate acoustic energy along the wave front. By modeling larger calculation ranges (20 km) and deeper deploying sources, the changing of the growth and decline of acoustic energy and lower acoustic mode amplitude by range, along the front of internal wave can be observed in this paper.

Underwater acoustic energy fluctuations during strong internal wave activity using a three-dimensional parabolic equation model

2019 ◽  
Vol 146 (3) ◽  
pp. 1875-1887 ◽  
Author(s):  
Georges A. Dossot ◽  
Kevin B. Smith ◽  
Mohsen Badiey ◽  
James H. Miller ◽  
Gopu R. Potty
Keyword(s):  
Parabolic Equation ◽  
Internal Wave ◽  
Three Dimensional ◽  
Equation Model ◽  
Wave Activity ◽  
Acoustic Energy ◽  
Underwater Acoustic

THREE-DIMENSIONAL ACOUSTICS EFFECTS IN THE ASIAEX SCS EXPERIMENT

2009 ◽  
Vol 17 (01) ◽  
pp. 11-27 ◽  
Author(s):  
YUNG-SHENG CHIU ◽  
YUAN-YING CHANG ◽  
LI-WEN HSIEH ◽  
MEI-CHUN YUAN ◽  
CHI-FANG CHEN
Keyword(s):  
South China Sea ◽  
Internal Wave ◽  
South China ◽  
Three Dimensional ◽  
Shelf Break ◽  
Nonlinear Internal Wave ◽  
Wave Refraction ◽  
China Sea ◽  
3D Effects ◽  
Ocean Environment

A three-dimensional (3D) ocean environment is assimilated with measured ocean data in the ASIAEX SCS (Asian Seas International Acoustics EXperiment, South China Sea) experiment. The experiment site is characterized as an active internal wave propagation region along the Northwestern shelf break of the South China Sea. Three-dimensional acoustics effects in the area are studied using FOR3DW, a wide-angle version of the parabolic equation code FOR3D (a Finite difference solution, an Ordinary differential equation, and Rational function approximations for solving 3D problems), and MOS3DPEF (MOdal Spectrum analysis based on 3D PE Field). The TL comparison between Nx2D and 3D calculations are shown to demonstrate the 3D effects. Variations in topography of the shelf break and in the water column due to the internal waves cause the 3D effects in the acoustic field. The intercomparison of the importance of bottom steering 3D effects and nonlinear internal wave refraction 3D effects is therefore proposed to realize which possesses the major part of the 3D effects. Also, 3D modal analysis results show that the nonlinear internal wave front causes severe horizontal refraction for higher modes.

Low-Frequency Acoustic Propagation Through Crossing Internal Waves in Shallow Water

2020 ◽  
Vol 28 (03) ◽  
pp. 1950013
Author(s):  
Alexey Shmelev ◽  
Ying-Tsong Lin ◽  
James Lynch
Keyword(s):  
Internal Wave ◽  
Shallow Water ◽  
Internal Waves ◽  
Three Dimensional ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Full Field ◽  
Wave Trains ◽  
Acoustic Ducts ◽  
Numerical Approaches

Crossing internal wave trains are commonly observed in continental shelf shallow water. In this paper, we study the effects of crossing internal wave structures on three-dimensional acoustic ducts with both theoretical and numerical approaches. We show that, depending on the crossing angle, acoustic energy, which is trapped laterally between internal waves of one train, can be either scattered, cross-ducted or reflected by the internal waves in the crossing train. We describe the governing physics of these effects and illustrate them for selected internal wave scenarios using full-field numerical simulations.

scholarly journals Mean flow generation by three-dimensional nonlinear internal wave beams

2019 ◽  
Vol 864 ◽  
pp. 303-326 ◽  
Author(s):  
F. Beckebanze ◽  
K. J. Raja ◽  
L. R. M. Maas
Keyword(s):  
Internal Wave ◽  
Three Dimensional ◽  
Theoretical Expression ◽  
Mean Flow ◽  
Production Term ◽  
Nonlinear Internal Wave ◽  
Vertical Vorticity ◽  
Flow Generation ◽  
The Mean ◽  
Vorticity Production

We study the generation of resonantly growing mean flow by weakly nonlinear internal wave beams. With a perturbational expansion, we construct analytic solutions for three-dimensional internal wave beams, exact up to first-order accuracy in the viscosity parameter. We specifically focus on the subtleties of wave beam generation by oscillating boundaries, such as wave makers in laboratory set-ups. The exact solutions to the linearized equations allow us to derive an analytic expression for the mean vertical vorticity production term, which induces a horizontal mean flow. Whereas mean flow generation associated with viscous beam attenuation – known as streaming – has been described before, we are the first to also include a peculiar inviscid mean flow generation in the vicinity of the oscillating wall, resulting from line vortices at the lateral edges of the oscillating boundary. Our theoretical expression for the mean vertical vorticity production is in good agreement with earlier laboratory experiments, for which the previously unrecognized inviscid mean flow generation mechanism turns out to be significant.

Supersonic flow over three dimensional cavities

2013 ◽  
Vol 117 (1188) ◽  
pp. 175-192 ◽  
Author(s):  
R. Das ◽  
J. Kurian
Keyword(s):  
Supersonic Flow ◽  
Shear Layer ◽  
Acoustic Waves ◽  
Layer Structure ◽  
Three Dimensional ◽  
Wave Structure ◽  
Acoustic Mode ◽  
Acoustic Energy ◽  
Acoustic Oscillations ◽  
Acoustic Signature

AbstractThis work presents a study of acoustic oscillations generated and the wave structure associated with supersonic flow past wall mounted 3D open cavities of varying length-to-width (L/W) ratio. Experiments were conducted to investigate the acoustic signature generated by the cavities at freestream Mach number of 1·7. The effect ofL/Wratio of the cavity on the dominant modes of the acoustic signature registered on different walls of the cavities is investigated for anL/Wrange of 0·83-4. Shift in the dominant acoustic mode is observed asL/Wratio changes from 3 to 4. Statistical analysis of pressure data showed existence of acoustic waves and spreading of acoustic energy over different modes with change in cavity width. Time averaged schlieren visualisation indicated variation of shock and shear layer structure in the mainstream for the different cavities. Acoustic waves generated by the presence of the cavity and the dynamic behaviour of the shear layer were observed during instantaneous shadowgraph visualisation. Numerical simulation was done to make a prior assessment of the flow structure and the results are in good agreement with those from experiments. Ratio of mass exchange between cavity and mainflow and the cavity volume was observed to have profound effect on the magnitude of pressure oscillations generated by the cavities.

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