Application Of Advanced Sectional Profiles In The Design Of Propulsors And Ship Appendages

In modern ship design problems related to cavitation can be solved successfully by properly designing the surfaces of propeller blades, rudders, shaft struts, etc. When the cavitation is of a limited nature, optimization of the geometry with respect to the inception of cavitation can lead to a significant reduction of the extent of the cavitation. This paper describes a practical method which is routinely used at the Maritime Research Institute Netherlands (MARIN) in the design process of sectional profiles of propeller blades, waterjet impellers, propeller shaft struts, fins and other hull appendages. The method is based on a parametric representation of the thickness and camber distributions in combination with a search algorithm and a two-dimensional panel method for analysis of the cavitation inception performance of the sectional profiles. Recent experience of MARIN is presented with the application of optimized sectional profiles in propeller blade designs and the shaft struts of high-speed vessels. The design method leads to excellent cavitation-inception properties, which is of particular importance for naval propellers. As long as the cavitation is of a moderate extent, the method is able to substantially reduce the risk of cavitation erosion and the magnitude of the hull-pressure fluctuations. However, there are also indications that, once the cavitation is fully developed, the use of the optimization procedure can lead to profiles with a higher risk of erosion and a more fluctuating cavitation.