Flow field and cavitation characteristics of hydrofoils coated with hydrophilic and hydrophobic polymers

Abstract

Tidal power turbines take advantage of tidal energy to generate renewable hydropower. Since the tidal turbines are fixed in the ocean, it is common to paint the blade and the structure of tidal energy generator with antifouling coating to prevent marine organisms from attaching to them. In this research, hydrophilic and hydrophobic coatings which are thought to be useful as countermeasures to prevent marine organisms’ adhesion are studied. We focused on the influence of the (hydrophilic and hydrophobic) coatings on the cavitation and flow field characteristics. The hydrophilic coated foil restrained the cavitation inception and growth compared to the hydrophobic coated foil from our experiment. And then, FFT was carried out on the pressure fluctuation measured in each coating foil, and the absolute value of the pressure fluctuation amount and the difference in the fluctuation period were clarified. And as another characteristic of the coated foils, the flow field near the coating surface was investigated. The velocity distribution near the foil’s surface was measured using Laser Doppler Velocimetry (LDV). In this experiment, a flat plate with or without the hydrophilic and hydrophobic coatings were used. As a result, differences in the boundary layer thickness and the velocity near the wall were revealed.