Experimental Study on Influences of Surface Materials on Cavitation Flow Around Hydrofoils

In order to resist on the cavitation erosion, many researchers try to change the solidity and tenacity of the coatings, but ignore the influence of surface characteristics of materials on cavitation flow and the interaction with each other. In this paper, high speed visualization system is used to observe the cavitation flow patterns in different stage. After comparing the characteristics of cavitation flow around hydrofoils made of aluminum (Foil A), stainless steel (Foil B) and the hydrofoil painted with epoxy coating (Foil C), the study shows that material has a significant effect on the cavitation flow. Firstly, when the incipient cavitation occurs, cavitation number of Foil A is highest among three hydrofoils, generating horseshoe vortex randomly. For Foil B and Foil C, it shows in the form of free bubbles. When the sheet cavitation occurs, Foil A has the highest cavitation number and shortest period, which is contrary to Foil C. And cavity consists of lots of small finger-like cavities. For Foil B and Foil C, it both constitutes with many bubbles. Compared with the high-density and small-scale cavities over surface of Foil C, the cavity of Foil B has larger scale and less density, which causes a minimal scope of influence of the re-entrant jet and strong randomness. When the cloud cavitation occurs, Foil C has the lowest cavitation number and shortest period. Secondly, compared with aluminum, both of stainless steel and epoxy coating restrains the occurrence and development of cavitation, and stainless steel and epoxy coating performs better than aluminum. For inception and sheet cavitation, stainless steel performs better than epoxy coating and aluminum. For cloud cavitation, epoxy coating performs better than stainless steel and aluminum. The objective of this paper is applied experimental method to investigate the effect of surface materials on cavitation around Clark-Y hydrofoils.