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.
- Presented at the Seminar on Ship Vibration, June 8-9, 1977.
Norske VeritasGrenseveien 92, Etterstad
Oslo 6, Norway
- Frivold, H
- Publication Date: 1977
- Pagination: 19 p.
- TRT Terms: Blade loading; Cavitation (Mechanics); Cavitation erosion; Excitation; Force; Hulls; Measurement; Propellers; Ships; Vibration; Wakes
- Old TRIS Terms: Hull forces; Hull propeller interaction; Model testing; Propeller excitation; Propeller induced vibration; Vibration measurement; Wake surveys
- Subject Areas: Design; Marine Transportation; Vehicles and Equipment;
- 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