翼型のクラウドキャビテーションの発生機構とその制御

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This paper describes the experimental result of cloud cavitation on a two-dimensional foil. Cloud cavitation was observed by a high speed camera and a high speed video camera to know the mechanism of cloud cavitation. Ink was injected to investigate the reserve flow (re-entrant jet) at the bottom of the sheet cavity. The flow around the sheet cavity was measured by a laser doppler velocimeter. By applying conditional sampling technique on the flow measurement, unsteady flow field was examined with the motion of cloud cavitation. A small square bar was attached on the foil surface and the effect on the cloud cavitation was investigated. The conclusion are as follows : (1) The shedding of cloud cavitation is caused by re-entrant jet. (2) The re-entrant jet starts at the rear center of a sheet cavity and spreads to the leading edge. The re-entrant jet disturbs the sheet cavity and the sheet cavity collapses into a mass of bubbly cavities. When the re-entrant jet reaches the cavity leading edge, the shedding of cloud cavity occurs. (3) A bar attached on the foil surface reduces the re-entrant flow, resulting in the reduction of cloud cavitation shedding. A ditch on the foil surface gives the similar effect on the cloud cavitation.
社団法人日本船舶海洋工学会の論文