Low-frequency acoustic scattering by gas-filled prolate spheroids in liquids. II. Comparison with the exact solution

1998 ◽  
Vol 103 (2) ◽  
pp. 822-826 ◽  
Author(s):  
Zhen Ye ◽  
Emile Hoskinson
Keyword(s):  
Exact Solution ◽  
Acoustic Scattering ◽  
Low Frequency ◽  
Prolate Spheroids

scholarly journals Simulation and analysis on low-frequency scattering characteristics of the finite cylindrical shell in shallow water

2019 ◽  
Vol 283 ◽  
pp. 03007
Author(s):  
Jinyu Li ◽  
Dejiang Shang ◽  
Yan Xiao
Keyword(s):  
Cylindrical Shell ◽  
Free Space ◽  
Acoustic Scattering ◽  
Low Frequency ◽  
Target Strength ◽  
Wave Direction ◽  
Scattering Field ◽  
Simulation Results ◽  
Finite Cylindrical Shell ◽  
Target Locations

Low-frequency acoustic scatterings from a finite cylindrical shell are numerically analyzed by FEM. The simulation results show that the acoustic-scattering field in waveguide has lots of frequency-related sidelobes, while no sidelobes exist in free space at low frequencies. The simulation also indicates that the module value in waveguide can be almost 20 dB larger than that in free space at low frequency, which is caused by the ocean boundaries. We also demonstrate that when the incident wave direction is normal to the target at low frequency, the target strength will be maximum and the distribution of the acoustic-scattering field is axisymmetric about the incident waving direction. Meanwhile, the acoustic-scattering field is also related to the impedance of the seabed, and the change of the impedance makes just a little contribution to the scattering field. Finally, the influence of different target locations is analyzed, including the targets near the sea surface, seabed and the middle region of the ocean waveguide, respectively. From simulation results, it is evident that the distribution of the acoustic-scattering field at low frequency has a little difference, which is smaller than 0.5 dB with various target locations, and the change is frequency and boundary-related.

Acoustic Scattering by Two Submerged Spherical Shells

1998 ◽  
Vol 06 (04) ◽  
pp. 421-434 ◽  
Author(s):  
Gordon C. Everstine ◽  
Guillermo C. Gaunaurd ◽  
Hanson Huang
Keyword(s):  
Exact Solution ◽  
Finite Element ◽  
Boundary Element ◽  
Series Solution ◽  
Spherical Wave ◽  
Acoustic Scattering ◽  
Element Model ◽  
Computer Code ◽  
Structural Acoustics ◽  
Coupling Coefficients

We validate, using a coupled finite element/boundary element computer code, a recently-developed1 series solution for the structural acoustics problem of scattering from two submerged spherical elastic shells. Although the general purpose computational tools for acoustic scattering have never been restricted to single scatterers, the availability of the series solution provides, for the first time, the mutual validation of both exact and numerical approaches for a multiple elastic scatterer problem. The excellent agreement between the two solutions presented thus allows this problem to be added to the short list of existing benchmark structural acoustics problems possessing an analytic solution. For the purposes of this comparison, the direction of incidence is taken as parallel with the axis joining the two shells. The numerical solution uses the NASHUA code, which couples a finite element shell model of the two shells with a boundary element model of the surrounding fluid. The exact solution is found by expanding in terms of classical modal series and uses the addition theorem for the spherical wave functions. The exact solution requires coupling coefficients that are expressed in terms of sums of products of Wigner 3-j symbols (or Clebsch-Gordan coefficients).

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