For calculating the vibration of the more localised structures of a ship, such as the machinery space, propulsion-shafting bearing supports, and deck houses, the finite-element method is more suitable than the idealislation of the ship as a system of beams. The Author describes the structural aspects of a finite-element model that was used in the prediction of the propeller-induced vibrations of a 150,000-shp triple-screw high-speed trailer-ship prior to its construction, and discusses and draws some conclusions from this application of the model. Mode shapes of the model show that, at operating-rpm blade frequencies, the hull does not vibrate as a beam in bending, shearing, and twisting; the decks and double bottom move with different wave lengths, amplitudes, and phases. Hull flexibility can significantly affect the transverse-vibration frequencies of the shafting system. The response of the model shows the importance of detuning the propulsion-system resonant frequencies from the operating rpm. It is suggested that the proper use of the finite-element method in the calculation of propulsion-system longitudinal vibration is not for the computation of a static longitudinal stiffness of the thrust-bearing foundation, but rather for the dynamic analysis of a model that includes the shafting system and appropriate hull structures.

  • Availability:
  • Corporate Authors:

    International Periodical Press

    193 Heemraadssingel
    Rotterdam,   Netherlands 
  • Authors:
    • Liepins, A A
  • Publication Date: 1978-5

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Filing Info

  • Accession Number: 00182488
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Oct 12 1978 12:00AM