Abstract
The paper is largely based on analysis of a series of experiments by Koushan (2006 I and II), where an azimuth thruster with open propeller is tested in conditions with intermittent ventilation. The use of a 6-component blade dynamometer on one of the four propeller blades gives detailed insight into the forces on the propeller, while the use of high-speed underwater video gives a visual understanding of the ventilation phenomena. Analysis of the propeller ventilation can be divided in two parts: aiming at classification of different types of propeller ventilation and typical thrust loss related to each of them, and the discussion of the ventilation inception mechanism based on the requirements for propeller to ventilate: i.e. propeller loading, forward speed and submergence.