Cavitation on Superhydrophobic Propellers

Cavitation characteristics are an important aspect of marine propeller performance. Cavitation caused by propellers is usually not desirable, and can cause pitting and erosion as well as unwanted noise. Altering the surface roughness on the propeller alters the cavitation dynamics. Experiments were done to characterize relative cavitation characteristics between one inch diameter superhydrophobic (SH) and smooth aluminum propellers. All propellers were polished, and SH surfaces were created by means of etching with sodium hypochlorite followed by treatment with hexadecyltrimethoxysilane. Propellers were placed in a water tunnel with low flow and rotated between 6000 and 20000 RPM. The propeller speed resulting in cavitation inception was found for each propeller. Cavitation inception is compared for both SH and non-SH propellers. Additionally, the location of cavitation inception at varied speeds was studied to determine the effect of SH surface treatment on propeller cavitation. Changes in torque coefficient between SH and non-SH propellers are also investigated as well as noise production.