Effect of internal inhomogeneities on acoustic scattering from finite cylindrical shell bounded by hemispherical endcaps

1999 ◽  
Vol 105 (2) ◽  
pp. 1088-1088
Author(s):  
Nicolas Touraine ◽  
Dominique Décultot ◽  
Gérard Maze ◽  
Aleksander Klauson ◽  
Jaan Metsaveer
Keyword(s):  
Cylindrical Shell ◽  
Acoustic Scattering ◽  
Finite Cylindrical Shell

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.

scholarly journals Acoustic scattering from a stiffened finite cylindrical shell with external rings

2019 ◽  
Vol 283 ◽  
pp. 03002
Author(s):  
Fulin Zhou ◽  
Jun Fan ◽  
Bin Wang
Keyword(s):  
Cylindrical Shell ◽  
Acoustic Waves ◽  
Cylindrical Shells ◽  
Acoustic Scattering ◽  
Approximate Analytical Expression ◽  
Low Frequencies ◽  
Stiffened Cylindrical Shell ◽  
Layered Shells ◽  
Underwater Target ◽  
Finite Cylindrical Shell

Studying the interaction of sound with cylindrical shells immersed in water is essential and helpful to improving underwater target detection and classification algorithms. Elastic cylindrical shells often occur as part of double-layered shell and have been widely used in marine and aerospace area. Acoustic waves are easy to be transmitted through the outer shell to the interior especially at low frequencies, thus directly being scattered by the inner shell and the rings in water between double-layered shells. Therefore, the externally ring-stiffened cylindrical shell is investigated in this paper. An experiment was conducted that measured the acoustic scattering. A hybrid 2-D/3-D finite-element modelling technique is employed to numerically calculate the scattering characteristics. Good qualitative agreement is found between numerical calculations and experimental measurement. An approximate analytical expression is given explicitly to identify the Bragg wave trajectories in the frequency-angle spectrum. It also has been shown that the rings not only affect the dynamic response of shell and indirectly influence the exterior scattered field, but also become direct acoustic scatterers in water and increase the target cross section especially at oblique incidence.

Vibrational and acoustic radiation from a submerged periodic cylindrical shell with axial stiffening

2009 ◽  
Vol 223 (5) ◽  
pp. 1083-1089 ◽  
Author(s):  
C-J Liao ◽  
W-K Jiang ◽  
H Duan ◽  
Y Wang
Keyword(s):  
Cylindrical Shell ◽  
Analytical Study ◽  
Acoustic Radiation ◽  
Sound Radiation ◽  
Mechanical Impedance ◽  
Stiffened Cylindrical Shell ◽  
Reaction Forces ◽  
Radial Forces ◽  
Vibration And Sound Radiation ◽  
Finite Cylindrical Shell

An analytical study on the vibration and acoustic radiation from an axially stiffened cylindrical shell in water is presented. Supposing that the axial stiffeners interact with the cylindrical shell only through radial forces, the reaction forces on the shell from stiffeners can be expressed by additional impedance. The coupled vibration equation of the finite cylindrical shell with axial stiffening is derived; in this equation additional impedance caused by the axial stiffeners is added. As a result, the vibration and sound radiation of the shell are dependent on the mechanical impedance of the shell, the radiation sound impedance, and the additional impedance of the axial stiffeners. Based on the numerical simulation, it is found that the existence of axial stiffeners decreases the sound radiation and surface average velocity, whereas it increases the radiation factor. The characteristics of the acoustic radiation can be understood from the simulation with good results, which show that the presented methodology can be used to study the mechanism of the acoustic radiation of the complicated cylindrical shell and to optimize its design.

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