The recently introduced D.o.T. Code of Practice for Noise Levels in Ships emphasises the importance of careful noise and vibration engineering at the design stage. To control noise and vibration in ships and marine structures, treatment at source is more satisfactory than treatment at the "receiver" areas, the other basic approach. Source treatments include the mounting of machinery on rafts; in this construction, there are two primary design-aims: minimisation of the ratio of dynamic mass to the total mass of the isolated installation, and reduction of the force transmitted through the mount to the ship's structure. Design in accordance with these aims may be done by finite-element dynamic analysis techniques; the geometry and physical parameters of ships and fixed structures are readily modelled, and super-element techniques facilitate the modelling of design changes. After giving some general information on these matters, the author, of Structural Dynamics Ltd, Southampton, discusses three typical applications of his firm's experience in the control of noise and vibration in ships and marine structures:--(1) Propeller cavitation which resulted in vortices, shed from the blades, collapsing on a ship's hull and causing both unacceptable noise levels in cabins and vibration that weakened the plate welds. It is considered that this problem should have been anticipated at the design stage, when larger blade-tip clearances and revised blade-loadings could have been incorporated. (2) Whole-body isolation of a superstructure, which is sometimes a feasible alternative to isolation at source. In the case discussed, a finite-element analysis was successfully carried out for an accommodation package (with an isolated mass of 2,400 tonnes) in a fixed offshore structure. (3) A dynamic analysis of a turbo-generator string support in a fixed offshore structure (the same principles could be applied to an installation in a ship). The analysis discussed is that of a 17,000-kW unit mounted across two modules; tabulated results are included. Order from BSRA as No. 50,006.

  • Corporate Authors:

    Whitehall Technical Press Limited

    29 Palace Street, Westminster
    London SW1,   England 
  • Authors:
    • Muir, R S
  • Publication Date: 1978-10

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Filing Info

  • Accession Number: 00194233
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: May 26 1979 12:00AM