AN OWNERS VIEW OF PROPELLER INDUCED VIBRATIONS
After an introduction in which he mentions the difficulty of avoiding propeller-induced vibration and noise in single-screw ships of very high power, and the need to consider, in the initial design stage of ships of conventional as well as high speed and power, the possibility that harmful vibration might occur, the Author (of A. P. Moller, Copenhagen) discusses these problems from a shipowner's viewpoint. Vibration velocity is more significant than acceleration or amplitude as a vibration parameter, and the inclusion, in the ISOD Draft Proposal "Interim Guidelines for the Evaluation of Vibration in Merchant Ships", of velocity as a parameter for judging vibration levels for frequencies above 5 or 6 Hz, is welcomed. The question of judging acceptable vibration levels is discussed in some detail, and it is suggested that it would be useful if owners and builders had a reference available containing actual vibration limits, preferably using RMS values of vibration velocities. The introduction of vibration levels based on the summation and weighting of the vibration spectrum, together with differentiation of acceptable levels according to the purpose of the location within the ship, seems reasonable. The relationship between vibration and noise is also discussed. Decision-making in the preliminary design stage is considered with particular reference to single-screw propulsion, and to the choice of a low propeller-speed. It is mentioned inter alia that some single-screw ro/ro ships built during the last few years have shown that wide flat after-bodies represent a special problem in propeller-induced hull-pressure fluctuations. Shipbuilders today are generally successful in avoiding resonant frequencies, but success has been less certain in estimating and avoiding harmful excitations from the propeller working in a wake. Some examples of these problems, and their consideration in the initial design phase, are discussed, including the design procedure adopted in a recent project for six 20,000-dwt cargo liners with stern ramps. Knowledge now being gained from analytic and experimental methods and shipboard measurements should be condensed into guidelines and practical procedures that will enable the ship designer to control the level of propeller-induced vibration from the beginning of the project. An excellent example of a step in this direction is B.S.R.A.'s "Design Guidance Note on the Avoidance of Propeller Excited Vibration Problems". Order from BSRA as No. 52,508.
- Paper presented at the Symposium on Propeller Induced Ship Vibration, London, 11-13 December 1979.
Royal Institution of Naval Architects, England10 Upper Belgrave Street
London SW1X 8BQ, England
- Kappell, J J
- Publication Date: 1979
- Features: References;
- Pagination: 6 p.
- TRT Terms: Cavitation noise; Excitation; Hulls; Propellers; Screw propellers; Ships; Vehicle design; Vibration
- Uncontrolled Terms: Ship design
- Old TRIS Terms: Hull propeller interaction; Propeller excitation; Propeller induced vibration
- Subject Areas: Design; Marine Transportation; Vehicles and Equipment;
- Accession Number: 00311530
- Record Type: Publication
- Source Agency: British Ship Research Association
- Report/Paper Numbers: Paper No. 1 Conf Paper
- Files: TRIS
- Created Date: Jun 26 1980 12:00AM