The experimental study of surface coatings' effect on cavitating flow around hydrofoil

Influence of surface coatings on cavitating flow around hydrofoil was observed through high speed visualization system. With decreasing of σ, the incipient cavitation, sheet cavitation, cloud cavitation were observed. When σ=1.50, the sheet cavitation occurred around Foil A!but incipient cavitation occurred around Foil B. When σ=1.19, sheet cavitation occurred and the cavity lengths around Foil A and Foil B were about the same. The collapsing of bubbles generated much horseshoe vortex, while the attached spot cavity around Foil A induced to large scale vortex. At σ=0.7, cloud cavitation occurred and the non-dimensional cavitation area around Foil A was relatively smaller. The vortex around Foil A shed regularly. The shed vortex around Foil B scattered in form of horseshoe vortex. The re-entrant flow induced the periodical shedding of large scale vortex and forming of vortex line.