Design and analysis of counter-rotating propellers-comparison of numerical and experimental results

In these last years a growing interest has been devoted to counter-rotating propellers especially for pod/stern drive applications for pleasure boats. In this context DINAV has been interested in the framework of an industrial R&D project to develop design/analysis computer codes for such kind of propulsors which is based on a modern lifting-line/lifting surface design method[1-4].The present work is devoted to the comparison between the foregoing numerical design/analysis tools and the results of the cavitation tunnel tests. The validation study has been performed on a set counter rotating propellers designed to be installed on a commercial pod drive system.Despite some uncertainty intrinsically connected to the nature of the test, results are very well in agreement with design points, allowing to validate the theoretical codes developed so far and to obtain semi-empirical correction factors for future application.