Experimental Analysis of Cavitation Erosion on Blade Root of Variable Pitch Propeller

The aim of this study is to experimentally investigate the cavitation erosion on the blade root of a model scale controllable pitch propeller. Tests are carried out in a cavitation tunnel, using the soft paint technique to study cavitation erosion, exploiting also two standard cameras and one high speed camera to study the damage patterns and cavitation dynamics, respectively. Standard cameras are placed on the top of test section in order to periodically monitor the occurrence of damages on the layer of paint. The high-speed camera has been used instead to analyse bubble dynamics and identify potentially erosive phenomena. Three different cavitation bubble structures on the blade root have been identified in the present study: streak cavitation, spherical bubble cavitation, and twisting bubble cavitation. The paint tests results have been analysed together with high-speed videos, showing a remarkable agreement between the occurrence of damage and cavitation collapse phenomena. The results demonstrated two regions on the propeller blade root with high risk of erosion: (1) suction side blade root showed significant damage pattern due to single bubble as well as bubble assembly collapse, and (2) pressure side blade root showed slight damage pattern due to spherical bubble collapse.