Dissertation > Transportation > Waterway transport > Marine Engineering > Ship Principle > Ship structural mechanics > Ship Vibration

Sensitivity Analysis of Vibration and Acoustic Radiation of Submarine Model

Author HuangPu
Tutor LiSheng
School Dalian University of Technology
Course Design and manufacture of ships and marine structures
Keywords Submarine model Fluid-structure interaction Finite elementmethod Boundary element method Finite difference method Acoustic radiation Sensitivity analysis
CLC U661.44
Type Master's thesis
Year 2013
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In anti-submarine warfare, submarine is mainly founded by detecting the radiated noise. The radiated noise is smaller, the submarine is less easy to being detected, therefore, the submarine’s acoustic shadow is most important indicators to measure its combat effectiveness. How to reducing the submarine’s radiated noise in navigation is always target that every country’s navy make great efforts to get. The noise reduction methods are reducing the vibration for dynamic systems and putting sound-absorbing material in the shell surface. In addition, we can also modify the structure parameters to achieve the purpose of reducing submarine radiated noise, this article is from this perspective to study the radiated noise of submarine structure.First of all, introduced the domestic and foreign scholars’research on the numerical calculation of structural acoustics, vibration and radiated acoustics of submarine structure, dynamic sensitivity analysis of structure and structure-acoustic sensitivity analysis of structure.Secondly, introduced the theory of fluid-structure coupling vibration, established a fluid-structure coupling model for submarine structure by using FEM software ANSYS. In low frequency range, calculated the first nine natural frequencies and shown the corresponding modes, also calculated vibration response displacement and vibration response speed of three nodes in the submarine outer shell.Moreover, introduced the acoustic theory and boundary element theory. Established the BEM model for submarine structure by using BEM software Virtual.Lab Acoustics, calculated the sound pressure level of near-field points and the radiated sound power level of submarine structure model, drawn out the sound pressure directivity figures and sound pressure color map in the yz plane. In the same condition, studied the differences of sound pressure level, radiated power level, radiated efficiency and radial quadratic velocity level between single shell and double shell for10Hz-500Hz. Explained that double shell could be useful to reduce the radiated noise of submarine.Finally, deduced formula of vibration response sensitivity and radiated acoustics. And then, using length of the inner(outer) shell, radius of the inner(outer) shell, thickness of the inner(outer) shell and floor as the design variables, the sensitivity of natural frequency, vibration response, sound pressure level of field point and radiation sound power level were computed by finite difference method. Explored influence of the different design variables to the different objective functions and got some useful conclusions.

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