Effect of superhydrophilic surface on the cavitation behaviors of rotating blades

Abstract

We experimentally confirmed the idea of mitigating (or delaying) the cavitation on the turbomachinery (rotating blades) by transforming the blade surface to be superhydrophilic, thereby the population of the cavitation nuclei is reduced near the surface. We focused on the changes in the cavitation incidence rate, amount of cavitation bubble, and bubble distribution on the superhydrophilic blade through the high-speed camera imaging, compared to the case with a regular (i.e., smooth) surface. With superhydrophilic blades, the cavitation incidence rate decreased significantly, indicating that fewer nuclei evolved into the actual cavitation bubbles. This is also associated with 8.6% delay of the critical rotational speed at which the cavitation process is almost completely established (incidence rate exceeds 80%), and the reduction in the total amount of cavitation bubbles was achieved as much as 18% (maximum 38% in the tested range of rotational Reynolds number). Additionally, the distribution of cavitation bubbles was generally pushed upstream, with fewer bubbles extending downstream, i.e., pushed away from the blade trailing edge. We believe the present results are promising enough to spur the follow-up investigation for the in-depth analysis and practical application toward the robust cavitation control without the substantial modulation of the geometry.