Abstract: Aiming at the cavitation and silt abrasion of hydraulic machinery,the study explores the mode of cavitation enhancing silt abrasion.The images of the distribution of cavity in flow of low silt content on the surface of hydrofoil are recorded by a system of laser-CCD at different cross-sections in the converging-diverging test section of the close-circulated apparatus.The law of the variation with time and the periodic behavior of birth,development,falling off and collapse of the cavity is acquired by analyzing the images.The grey distribution of the average value and the standard variation of the vapor cloud volume at different sections are obtained by using a statistical image processing method,and the latter represents the distribution of the velocity of the change of the vapor cloud volume.Referring to the published results of cavitation and silt abrasion,the study indicates that the mode of cavitation enhancing silt abrasion is depended on the distribution law of the cavity and the velocity of the change of the vapor cloud volume in the flow field of hydraulic machinery.

Key words: hydrofoil, cavitation and silt abrasion, multiphase of solid and liquid, cavity, image processing method