PROPELLER CAVITATION AND EXCITATION CONSIDERATIONS FOR LARGE TANKERS
In the past the trend of most ship designs turned towards higher speeds and larger displacements. Many modern cargoliners have cruising speeds close to, or in excess of 30 knots, and tankers with a displacement exceeding 250,000 dwt are in service on many trade routes. A consequence of this trend is the ever increasing power absorbed per propeller shaft. It is not surprising therefore that the propulsion aspects of these ships often pose severe problems. In particular, problems associated with propeller cavitation have become matters of great concern and also attention has to be paid to the propeller-induced forces on the shafting. The investigation presented in this paper comprises: (1) calculation and observation of cavitation behaviour; (2) calculation of dynamic propeller shaft forces; and (3) measurement of propeller-induced pressure fluctuations on the hull, of a restricted draft tanker of 475,000 tdw. The measurements were carried out in the Depressurized Towing Tank of the NSMB. The aim of this study was to determine the effect of camber and pitch of screw propellers in connection with propeller-hull interaction phenomena. From the results presented it is clear that the trade-off between pitch and camber in propeller design is important for the occurrence of cavitation and subsequent hull excitation considerations. It is demonstrated that whereas a relatively high pitch will always lead to sheet cavitation on the suction side, due to relatively high angles of attack of the flow, the subsequent influence on hull excitation is nevertheless more constant. The tendency is that the peak-to-peak values in such a case are smaller than the respective values for a design in which the camber is relatively high and the pitch is relatively small. In the latter case the occurrence of cavitation is less, but when it occurs the cavity is very large and unstable due to the relatively low pressure distribution along the whole blade section.
- Presented at the 1974 West European Conference on Marine Technology. Available as complete volume at $50.00 (10 papers).
Marine Media Management, Limited76 Mark Lane
London EC3R 7JW, England
- Oosterveld, MWC
- Verdonk, C
- van der Kooy, J
- Van Oossanen, P
- Publication Date: 1975
- Pagination: 4 p.
- West European Conference on Marine Technology (74)
- Publisher: Marine Media Management, Limited
- TRT Terms: Cavitation (Mechanics); Cavitation erosion; Hulls; Propeller shafts; Propellers; Vibration
- Old TRIS Terms: Hull propeller interaction; Propeller induced vibration; Propeller shaft vibration
- Subject Areas: Marine Transportation; Vehicles and Equipment;
- Accession Number: 00099935
- Record Type: Publication
- Source Agency: PTJ Publishing Incorporated
- Files: TRIS
- Created Date: Oct 18 1975 12:00AM