涂层对绕水翼云状空化的运动特性及动力特性影响的试验研究

Different experimental techniques are combined to carry out the flow patterns, kinetic and dynamic characteristics of cloud cavitation around three different coating hydrofoils and discuss the influence of different coatings. Three different coatings are smooth epoxy coating(Hydrofoil A), smooth fluorocarbon coating(Hydrofoil B) and rough fluorocarbon coating(Hydrofoil C). The results show four main phenomena. Firstly, coatings' roughness and material both effect the flow characteristics of cloud cavitation. Secondly, different coatings have different flow patterns. The comparison among cavities over hydrofoils with three different coatings verifies that Hydrofoil A has thinner thickness of attached cavity, more transparent cavity region, larger growth rate of cloud cavity and shorter period. Thirdly, coating effects the kinetic characteristics of cloud cavitation. For different coatings, positions of local low-speed region are different, resulting in positions of accumulation of transparent bubble are different, the same to the local positive vorticity region for the reason of the vortex vapor mixing region. In terms of variation range of transparent cavity, Hydrofoil A has smaller range than Hydrofoil B and C. In terms of positions of vortex vapor mixing region, Hydrofoil A has the shortest distance to the leading edge. Fourthly, compared with roughness, material of coating has more obvious effect on the dynamic characteristics of cloud cavitation. The dominant frequency of lifts of hydrofoils with different coating is different in cloud cavitation, which consistent with changes of cavitation flow structure. When develops into cloud cavitation, Hydrofoil B has the lowest cavitation number among three hydrofoils. So restriction on cloud cavitation generated by Hydrofoil B is stranger than Hydrofoil A and C.