Experimental investigation of vortex generator influences on propeller cavitation and hull pressure fluctuations

In this paper, the transient turbulent cavitating flow around a marine propeller behind a ship was investigated experimentally with emphasis on how vortex generator (VG) influences propeller cavitation and hull pressure fluctuations. The experiments were carried out in China Large Cavitation Channel with the closed test section covering 10.5 m in length and cross-section of 2.2 m(2) x 2.0 m(2). The experiment recorded instantaneous cavitation photos of the propeller and pressure fluctuations on the hull surface. The results demonstrate that without vortex generator, the sheet cavitation inception begins at -50 degrees (310 degrees), and then from -50 degrees (310 degrees) to 30 degrees, the extent and area of sheet cavitation increase. When vortex generator installed on the hull, the sheet cavitation inception occurs in advance at -60 degrees (300 degrees), and the sheet cavitation expands to larger rotation range due to the vortex generator. It is shown that the vortex generator with proper geometry and installed location may contribute the highly nonuniform wake to be more uniform, and can make the change of propeller cavitation to be milder, which decrease the pressure fluctuations in this study. Further analysis indicates that the vortex generator may promote the energy distribution to be more uniform in physical and spectral space in some degree.