VIBRATION EXCITATION FORCES

The most important vibration excitation forces are induced by the propeller. From a number of propeller blade loading calculations an estimate of the magnitude of shaft forces is obtained. The dynamic thrust is the most important shaft force from a ship vibration point of view. Measurements of propeller-induced hull pressure fluctuations provide a basis for an estimate of the vertical hull force, which, from the results presented is shown to be in the range 5-25% of mean propeller thrust. To reduce the excitation forces, a careful design of ship lines and of the propeller is necessary. Some tentative guidelines for the afterbody hull lines are given which may reduce the wake field peak on conventional single-screw ships. The need for wake field surveys and interactive propeller analysis with respect to cavitation performance is emphasised. The methods for prediction of excitation forces are described. The reliability of prediction is heavily dependent on the accuracy of the model wake field. An example shows that different model tanks and different measuring equipments produce dissimilar nominal wake fields for one and the same ship. Full scale experience is an important factor in DnV prediction methods and further research. Order from: BSRA as No. 49.082.

  • Supplemental Notes:
    • Presented at the Seminar on Ship Vibration, June 8-9, 1977.
  • Corporate Authors:

    Norske Veritas

    Grenseveien 92, Etterstad
    Oslo 6,   Norway 
  • Authors:
    • Frivold, H
  • Publication Date: 1977

Media Info

  • Pagination: 19 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00182471
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Report/Paper Numbers: Paper No. 5 Proceeding
  • Files: TRIS
  • Created Date: Sep 27 1978 12:00AM