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Research Papers

Reduction of the Sound Pressure Radiated by a Submarine by Isolation of the End Caps

[+] Author and Article Information
Mauro Caresta

School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW 2052, Australiamaurorestaca@yahoo.it

Nicole J. Kessissoglou

School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, NSW 2052, Australia

J. Vib. Acoust 133(3), 031008 (Mar 29, 2011) (7 pages) doi:10.1115/1.4003198 History: Received November 06, 2009; Revised August 04, 2010; Published March 29, 2011; Online March 29, 2011

A passive isolation approach to reduce the sound pressure radiated by a submarine is presented. The submerged vessel is modeled as a stiffened cylindrical hull partitioned by bulkheads and with two end caps of conical shape. Fluctuating forces from the propeller are transmitted to the hull through the shaft and a rigid foundation, resulting in axisymmetric excitation of the hull. The hull surface motion is mainly in the axial direction with a small radial component due to the coupling between the two orthogonal shell displacements. The sound pressure resulting from the axial motion is radiated from the end caps of the submarine. This work investigates reduction of the far field sound pressure by passive isolation of the end caps from the main hull. Isolation of the axial motion of the end caps from the cylindrical hull results in significant reduction of the radiated sound at low frequencies. The fluid loading approximation for a finite cylindrical shell in the low frequency range is also discussed.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 3

Real solutions of the nondimensional axial wavenumber for a cylindrical shell in water

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Figure 4

Amplitude ratio for a cylindrical shell in water

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Figure 5

Isolines for the real part (thick line) and imaginary part (thin line) of the characteristic equation for a fluid loaded steel cylindrical shell (Ω=0.38)

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Figure 6

Coordinate system and positive direction of the forces for the shaft

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Figure 7

Isolation of the conical end cap from the main hull

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Figure 8

Isolation of the conical end cap from the main hull

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Figure 9

Sign convention for the forces, moments, displacements, and slopes of the cones, cylinder, and circular plates

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Figure 10

Directivity pattern at the first axial resonant frequency of 22.5 Hz for a rigid connection between the cones and the cylinder

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Figure 11

Directivity pattern at the second axial resonant frequency of 43.5 Hz for a rigid connection between the cones and the cylinder

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Figure 12

Directivity pattern at the third axial resonant frequency of 70.0 Hz for a rigid connection between the cones and the cylinder

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Figure 13

Maximum sound pressure level for a rigid connection between the cones and the cylinder

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Figure 14

Percentage contribution of the conical end caps to the maximum sound pressure level for a rigid connection between the cones and the cylinder

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Figure 15

Maximum sound pressure level for isolation between the cones and the cylinder

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Figure 16

Difference of the maximum SPL for the case of a rigid connection and isolation between the cylinder and the cone, mean value (dashed-dot line)

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Figure 17

Axial displacement at the cylinder/cone junction (2)

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Figure 1

Submarine hull model

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Figure 2

Real solutions of the nondimensional axial wavenumber for a cylindrical shell in vacuo

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