High-speed visualization of cavitation evolution around a marine propeller

Nowadays, a lot of types of digital high-speed video camera are available with a wide range of image rates. The new camera technology has made it possible to observe the cavitation on a propeller. However, until recently cavitation on ship propellers is observed visually using the so-called time-lapse observations. The conventional time-lapse method cannot accurately detect the temporal development of cavitation. High-speed video visualizes the complete process of cavitation. A high-speed video system was developed to observe the cavity dynamics in more detail in a more reliable way. This paper shows the high-speed visualization results of a cavitating propeller, which give a better recording of the complete cavitation dynamics. Appropriate post-processing of the obtained high-speed images enables the detailed illustration of the interface topology of the propeller cavitation, and the weak tip vortex cavitation which is not readily apparent to the naked eyes can be detected by the edge-detection methodology. This can be used to explain the major discrepancies between acoustic criterion and optical criterion of detection of cavitation inception, which are known to provide different answers in the most practical applications.