Abstract

This thesis investigates the impact of superhydrophobic (SH) surface treatments on the cavitation behavior of small-scale marine propellers. Cavitation, the formation of vapor cavities in liquid due to local pressure reductions, can lead to efficiency losses, noise, and structural damage in marine propulsion systems. Although SH surfaces have shown promise in reducing drag and altering nucleation behavior in static or low-speed flow contexts, their effect on cavitation onset in rapidly rotating propellers remains underexplored. To address this, eight 1-inch aluminum propellers were tested, including variations in pitch, solidity, and blade number. Each design was produced in two versions: one treated to be superhydrophobic through a chemical etching and silanization process, and the other rendered hydrophilic with matte acrylic coating. Propellers were spun at cavitating speeds in a closed-loop water tunnel, and cavitation behavior was observed across a range of rotational speeds from 4500 to 15000 RPM. High-speed imaging, hydrophone data, and motor torque measurements were used to evaluate the inception and characteristics of cavitation. Image processing techniques and frequency-domain audio analysis were applied to track cavitation onset and identify acoustic signatures associated with cavitation phenomena. Preliminary results suggest that SH surface treatment influences the location and onset speed of cavitation, with SH-treated propellers exhibiting tip vortex cavitation later compared to their hydrophilic counterparts. These findings contribute to the understanding of how surface microstructure and wettability affect cavitation inception in high-speed marine applications. The results have implications for the design of more efficient and resilient propeller systems, especially in contexts where cavitation performance is critical.

Degree

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

https://lib.byu.edu/about/copyright/