In most cases it is necessary to have a mathematical model of a ship to predict mode shapes and frequencies. If the structural form of the vessel is simple and the beam analogy is applicable, then the model can be simple. However, as the structural complexity of the vessel grows the size of the model must grow too, until a full finite-element analysis is required. The properties of the model can then be changed at the design stage to predict an efficient way of reducing vibrations. If the ship already exists, then field measurements can be made and the model changed to duplicate them. The model can then be used with greater confidence to predict the future behaviour of the modified vessel. The Author discusses the motions set up by pulsating machinery and, to a less extent, by impact. Engine and propeller-induced vibrations are periodic in that they repeat themselves for hours on end. Impact vibrations from slamming, collision, or armaments occur suddenly and die away fast. Both types deform the hull, the only difference is the type of force that is applied and its variation with time. The peculiar problem of a trimaran is considered. Order from BSRA as No. 49,336.
- Paper presented at meeting of Pacific Northwest Section of SNAME, October 1977.
Society of Naval Architects and Marine Engineers601 Pavonia Avenue
Jersey City, NJ United States 07306-2907
- Hooley, R F
- Publication Date: 1977
- Pagination: 24 p.
- TRT Terms: Engines; Finite element method; Hulls; Machinery; Mathematical analysis; Mathematical models; Measurement; Propellers; Set forward force; Ships; Vibration
- Old TRIS Terms: Engine vibration; Hull vibration; Machinery vibration; Propeller induced vibration; Vibration measurement
- Subject Areas: Design; Marine Transportation; Vehicles and Equipment;
- Accession Number: 00185325
- Record Type: Publication
- Source Agency: British Ship Research Association
- Files: TRIS
- Created Date: Jan 13 1979 12:00AM