International Shipbuilding Progress - Volume 23, issue 266

Authors: Andersen, P.

Article Type: Research Article

Abstract: Lifting-line theory for calculating the characteristics of a supercavitating propeller is derived. The theory makes use of induction factors and is applicable for propellers of normal supercavitating geometry and for non-zero cavitation numbers. By comparison with model tests correction factors are developed to improve the numerical results and to correct for the the shortcomings of the lifting-line theory. Results are shown from calculations in which the propeller data are varied systematically thus making a small propeller series.

DOI: 10.3233/ISP-1976-2326601

Citation: International Shipbuilding Progress, vol. 23, no. 266, pp. 319-328, 1976

Authors: Beek, G.H.M. | Heidemans, J.

Article Type: Research Article

Abstract: Strength calculations for propellers are usually made using nominal static load values with fluctuations due to circumferential wake field variations superimposed. The allowable load is determined by applying experimentally obtained material properties (Smith/Goodman – diagrams) on the computed stress pattern. Moreover dimensions of propeller blades have to satisfy the requirements of the involved classification society. For special purpose applications (ice breakers, warships) discussion is mostly dominated by a compulsory strengthening of some components aiming at a higher survival rate in unpredictable conditions. Poor engineering judgment in applying these heavy duty requirements can lead to constructions where strength …levels at several critical spots are badly harmonized. This can lead to severe damage to propeller, shaftline, gear box or even the hull. While accepting that damage caused by excessive shock loads (grounding, extreme ice load) cannot always be avoided it is possible to restrict it by a suitable distribution of local strength over all the parts concerned. For a controllable pitch propeller the replacement of a single blade is a relatively simple operation, so the strengthening of other threatened parts in order to withstand the maximum load of a collapsing blade is an obvious consequence. This publication compares results of this philosophy with the classification societies’ rules. Stress calculations performed with the aid of modern numerical methods contributed to obtaining detailed information about stress conditions in complex shaped and loaded parts. Show more

DOI: 10.3233/ISP-1976-2326602

Citation: International Shipbuilding Progress, vol. 23, no. 266, pp. 329-341, 1976

Authors: Nilsson, Gunnar | Restad, Kjell

Article Type: Research Article

Abstract: A ship with her engine and propeller forms a system with a high degree of complexity. The shipbuilder has to accept contractual obligations regarding speed and revolutions. Vibrations under service conditions have always existed and been tolerated to a certain extent. The last years, however, have meant to the shipowner increasing difficulties to get his ship manned, and more attention is therefore paid to the shipboard environment. Cavitation damage to propellers has been known for a long time. With larger ships and the higher horsepowers of today’s ships, cavitation has unfortunately become a problem for many shipyards, propeller manufacturers and …owners. The above focuses upon some aspects of full scale propulsion related to the interaction between hull and propeller, which will be discussed further in the paper. We will deal only with such areas where, in our opinion, today’s knowledge is not complete enough and where further research is needed. The intent has been to produce a paper of a general nature in order to stimulate discussion. The paper is illustrated with Figures, most of which are actual model or full scale results. Show more

DOI: 10.3233/ISP-1976-2326603

Citation: International Shipbuilding Progress, vol. 23, no. 266, pp. 342-352, 1976