DAMPING IN PROPELLER-GENERATED SHIP VIBRATIONS

From full scale measurements it follows that for the lowest natural frequencies of a ship hull girder the damping is negligible, whereas in the blade frequency around service RPM the response is practically constant. It is shown that this phenomenon is adequately described by assuming a viscous damping which is proportional to the stiffness. By response here is meant the frequency function of the vibratory displacement amplitudes generated by a constant excitation. The response will generally not seriously be affected by the structural arrangement. This means that if information with regard to the response is available from comparable ships, the vibratory behavior is directly given by the propeller-induced excitation level. Therefore, in these cases the vibration investigations primarily have to be directed in minimizing the excitation forces. Only local structures need to be analyzed with regard to their vibratory behavior for each ship individually. It is difficult, however, to indicate the boundaries at which the local structures can be thought to be uncoupled from the overall vibrations with regard to their own vibrational behavior. Means are given to determine these boundaries. In this respect account has to be taken of the increased effect of damping with a larger complexity of the vibration pattern. With regard to the shaft vibrations several parameters are considered, showing the paramount role of the propeller coefficients. These are the hydrodyanmic effects of the vibrating propeller, such as the added mass of water. Also the effects of oilfim and gyroscopy are treated.

  • Corporate Authors:

    Netherlands Ship Model Basin

    Haagsteed 2, P.O. Box 28
    Wageningen,   Netherlands 
  • Authors:
    • Hylarides, S
  • Publication Date: 1975

Media Info

  • Features: References;
  • Pagination: 89 p.
  • Serial:
    • Issue Number: 468

Subject/Index Terms

Filing Info

  • Accession Number: 00099882
  • Record Type: Publication
  • Source Agency: Netherlands Ship Model Basin
  • Files: TRIS
  • Created Date: Sep 30 1975 12:00AM