Cavitation induced rudder erosion has become a major concern within the last years, especially for semi balanced rudders, due to the increased ship speed and propeller loading. Numerous attempts have been made by ship owners, yards, model basins and Class Societies to find short term practical solutions as well as improvements in the design. The problem, that countermeasures work well in some cases and in other applications not, is still not solved due to the lack of a full understanding of the erosion mechanism. However, a number of countermeasures is available to improve the situation. These solutions can be categorized into two approaches: 1. Control the hydrodynamic characteristics by altering the flows and/or geometries. Examples are full-spade rudder, whose upper and lower sections are twisted in opposite directions, horn type rudders with guide plates and/or slit bars in the gap area and a curvature of the bottom at the leading edge of the rudder blade. 2. Change the material resistance against the erosion without any change of hydrodynamic characteristics through a reinforcement of the material or the introduction of soft covers with using of neopren, epoxy based coatings or liquid metals. At the moment the experience is still not sufficient to guarantee that the rudder survives a class period of five years. Such experience will be available in a few years, based on the results gathered with different applications of countermeasures currently introduced. However designer and ship owner expect that the problem is solved by a complete theory and respective cavitation erosion prediction methods in connection with CFD tools. For this purpose essential efforts with research projects and model/full scale investigations are necessary and are going on at the moment in a combined action of owners, model basins and classification societies.
Cavitation induced erosion on rudders
HANSA. International Maritime Journal ; 142 , 12 ; 44-47
2005
4 Seiten, 6 Bilder, 7 Quellen
Article (Journal)
German
SCHIFFBAU - Research & Development - Cavitation induced erosion on rudders
Online Contents | 2005
|Cavitation Erosion on Ship Propellers and Rudders
British Library Conference Proceedings | 2004
|British Library Conference Proceedings | 1995
|Tema Archive | 1995
|Engineering Index Backfile | 1902
|