| Observation Of Collapsing Root-Cavitation Using a High-Speed Video Camera |
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| Root cavitation
phenomena on a propeller model was filmed with a high-speed video camera
(HPV-1, Shimazu Corporation). The camera can record 1000000 frames per
second at maximum frame rate. Condensation and re-expansion of the cavity
are observed clearly in the captured images. The experiments were carried out in the Large Cavitation Tunnel, National Maritime Research Institute of Japan.Photograph below shows the arrangement of the experimental instruments. |
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| This is one
of the experiments for the study on prevention of root erosion. The experiment was conducted to understand the behavior of the cavitation which caused root erosion. It is well known that cloudy cavitation around the root of propeller blades occurs and this type of cavitation, root cavitation, causes serious erosion. The surface of the propeller is damaged in the shape of a pockmark at an intial stage of the erosion. The blades of the propeller can be broken as the erosion is worse. We suggest a method to equip a small fin in front of the propeller for preventing root erosion. This fin is called Pre-Propeller Fin, PPF. The picture below shows the appearance of the propeller and the cavitation in the Large Cavitation Tunnel. In this case, the PPF is not installed. In this picture the blue arrow represents the root cavitation. We recorded the behavior of the root cavitation. Recording area is shown as a red rectangler in this picture. |
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| Click the icons blow, you can see the
examples of the movies. (format: avi, file size 600KB-2MB). |
 8,000images/s |
16,000images/s |
32,000images/s |
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| 63,000images/s |
125,000images/s |
250,000images/s |
| 500,000images/s |
1,000,000images/s | |
| (2006.2.6) |
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